Taking in patterns is not Ne. What you've just described I would consider more Fe--you're recognizing relationships between people and how they fulfill different roles:
Ne is more like this:
When I see people saying things like "oh well I use Ne and Ni equally well all the time!", I can't help but feel that they don't understand what those terms mean well enough to make that distinction. Their justification is almost invariably, "Well the function test said so!!!", which is all but meaningless.
I don't mean to sound pedantic, but I suggest you check out some more of the literature on this topic. The function attitudes are pretty convoluted at times and quite difficult to discern in practice. They don't represent individual actions but prevailing attitudes that lead us toward all of our perceptions and judgments of reality. "I noticed a pattern" doesn't mean "I used Ne." What you described above doesn't really constitute Ne at all.
I don't think it's impossible for Ni users to use Ne and vice versa, just that it doesn't happen very often and takes a lot more effort than people think it does. It requires breaking out of your perceptual mold and looking at things from a standpoint that you're not used to. Most people who think they're adept at all the functions simply don't understand the function attitudes well enough to know the difference.
Evidently you have some theoretical holes in your understanding of the functions which leads you to incorrectly associate certain actions with "uses" of certain functions. I'm not sure how to say that without sounding condescending, but I think it's the case. What books have you read on this topic?
The best thing I can advise you to do is look at why
people do what they do instead of worrying about the surface action. Keep trying to reduce every action/belief in others further and further until you arrive at axiomatic principles the person considers fundamental to how life should be understood, interpreted and dealt with.
"I noticed a pattern in something" could be any function depending on context and the motivations and values of the person in question.
The problem with this is that you can navigate most life circumstances just fine without really depending on shadow functions. The reason for the "stressful circumstances" explanation is that using shadow functions actually requires you to break out of your preferred worldview and see things from a perspective that is unnatural and uncomfortable to you.
It's not just using some other skill--it's actually changing the way you interpret and deal with yourself and your surroundings, and that's not easily done.
Please, if you want to move forward with this, just disregard tests entirely. This is a concept that lacks empirical evidence to the point that it can't be tested reliably at all. If you really want to know people's types, you have no choice but to study the functions and the value systems they most commonly associate with. Tests are not going to help you do anything more than get a very rough idea of which type categories to focus your personal studies on so that you can start figuring out which ones you identify most closely with. Tests are a sketchy and frequently inaccurate shortcut.
Tests are not all we really have. Your observation that most people tend to be very good at both attitudes of the same preference is rooted in an error in your understanding of the different attitudes. (I don't mean any offense by this.)
To give you a real life example, look at the way TJs tend to disregard anything that can't be understood and tested according to universally applicable empirical standards. Te requires that everyone be able to apply the same test in the same way and get the same consistent, measurable result.
In order to "use Ti", the Te user has to temporarily abandon Te's need for measurable, empirical evidence and accept an impersonal judgment purely on its own internal merits. This is very hard to most TJs to do, and I must strongly disagree that most of them are good at it.
This is sharply in contrast with the way TPs tend to build and interpret logic systems. Any way of organizing and looking at information that helps our understanding of how to navigate situations as they unfold is useful, as long as its rules are internally consistent with themselves. Ti doesn't really mind if its rules and judgments can't be demonstrated empirically or validated by external means.
In order for the Ti user to "use Te", he has to temporarily abandon his personal, situational understanding of the dynamics of a situation and trust externally imposed standards over his own direct experiential understanding of how something is supposed to work. This is very hard to do and I disagree that most Ti users are good at it.
You see, using a different function is not just performing a different surface action. It's actually warping the attitude with which we approach interpreting and responding to ourselves and the world around us. That is a very big change. It's literally breaking your bubble about how to conceptualize reality.
If an Fi user wants to "use Fe", for instance, he has to set aside his own subjective values in favor of integrating into the social and cultural standards of whatever group he's part of. That's very hard for Fi-ers to do--it often feels like they're not being true to who they really are. It takes some serious maturity and concern for the perspectives of others--it's not something that happens all the time.
You still seem to be associating function use with particular actions. e.g., I saw a pattern so I must have used Ne, or I made an impersonal decision so I must have used Ti, etc...the functions don't represent singular actions. They represent the most fundamental starting points from which people build their entire conceptions of reality.
You might very well be good at some individual skill that many Ne users are good at, but that doesn't mean you're necessarily using Ne to do it. "Using Ne" doesn't just mean "performing some action that Ne people tend to be good at"; it implies approaching and understanding reality from a certain perspective.
Again I will suggest that you read more material on what the function attitudes actually imply about the most fundamental ways people conceptualize reality. Based on your earlier description of your "Ne use", you don't seem to have a firm grasp on what "Ne use" actually is.
I'm not saying you never use Ne, just that it's not nearly as natural or commonplace as you think. Your criticisms that the current functional theories are inadequate are based largely in gaps in your understanding of the nature of cognitive functions themselves.
Getting things done doesn't constitute Te use. Going to school and mothering don't force you to be good at Te. These tasks can be accomplished just as well from the perspectives of lots of other functional attitudes (although the most closely related one is Fe, which is probably the case for you.)
Finding patterns =/= using Ne.
I think your issue with the shadow thing is rooted in the way you're conceptualizing functions as singular, particular actions instead of overarching, widely encompassing attitudes. You seem to think, "Ne is finding patterns, and I find patterns, so I must use Ne when I do that!", but it's a lot more complicated than that.
What exactly does being "good at" a function mean? It doesn't mean that you're good at tasks people strong in that function are usually good at; it means the way that function leads you to conceptualize reality comprises a larger part of your total worldview than other functional attitudes.
I think you're taking issue with being told your type isn't good at Ne or Te or whatever because you think you're being told you can't find patterns or plan and organize or whatever other common actions you associate with those functions. But those functions represent attitudes about how to consider yourself and your relationship to reality, not particular actions.
When someone says something on the forum, for instance, and others say, "Wow that was totally Si" or whatnot, they're not saying "The act itself of saying that was use of Si"; they're saying, "I believe the value that motivated you to say/do that was rooted in the worldview represented by Si." That's a BIG difference.
It would be nice to have neat little 20-minute questionnaires that solve the problem of identity for you; unfortunately that's never really going to happen because the tests can't get enough in-depth information to say much of anything meaningful. You cannot use tests to determine which of your functions are strong or weak or need improvement.
Think of it this way--imagine you've never heard any music and you want to know what kind of music you would like. Somebody points you to a 70-question internet quiz that will ask you about the types of sounds you find pleasing and then tell you which kind of music is your favorite. This will probably give you a decent starting point for your personal study of music, but does it actually necessitate that, once you go and listen to a lot of different kinds of music, your favorite will be the one the test told you? No, it doesn't, because there's no shortcut to figuring out what kind of music really suits you without listening to a lot of different music and figuring it out through direct experience and gradually developing a working understanding of the relationships between different approaches to music and how they relate to you. The same applies to understanding different approaches to cognition.
The only way to do this is to identify people who are
heavily influenced by those functional attitudes and talk to them about the ways they understand themselves and their environments and try to discover how they differ from yours. What basic assumptions about the nature of life, the universe and everything does this person make that lead him to think and behave the way he does, and what can you learn from them?