I may be totally missing what you are asking, so feel free to clarify if I miss the mark. I think struggling with that "social/intimate split" (as you put it) is the definition of Sx-last. My emotional/intellectual expression as an Sx-first 4w5 has an almost involuntary way of manifesting when it wants to-- in the moment, it doesn't really consider others or my own shame (which is why Sx 4 is called "shameless" at times). Self control is a discipline I've had to invest in the healthier I've become, to channel that energy and use it for good.
Nope, we're on the same page. What's funny is that out of my immediate family (in which I suspect
all of us are sx-last!), I am the most like what you describe in this paragraph, perhaps because of 4. Because of this, I had an sx-like self-image when I was younger that slowly got refuted as I moved away and got to know a wider range of people, many of whom wish they were less impulsive. What different life it would be that leads someone to work for that rather than the opposite of
more immediate expression, and yet I can still relate to some of them over having the same core type. It's just that one of us is inside out.
I have a theory that sx-last is the type most prone to being misunderstood as contrived when they express their emotions, but I'm blocked for now on explaining how this works.
But back to the topic at hand: your hesitation to speak up about something that bothers you in social settings is completely characteristic of 4 minus Sx, which equals unbuffered shame. 4 is full of shame, which I suspect is what keeps you from speaking in those moments. It has everything to do with instinctual variants.
This exactly answers my question.
As Sp/So you are the 4 that is long suffering to a point but sometimes suffers vocally.
I consider my first and second instinctual variants to be very close in strength, which in my experience expresses as a more balanced push/pull between these two tendencies affected by level of health and situation. When reading about what variants look like through specifically a 4 lens, often I'll be stumped between sp-first and so-first. What breaks the tie in the end is going back to what the basic triggers of the variants are regardless of type. I see them as a series of three locked boxes nested within each other, the one on the outside being sp and the one in the core being sx, and the unlocking of a box meaning that I've become confident (in my own 4-colored way) in the respective instinctual sphere. sp must be unlocked before any of the others, and sx only after the others. Another guiding question that seals sp-first is: if you could only satisfy one instinct, which would you be the most psychologically functional living on whilst totally deprived of the other two?
You feel an obligation to bite your tongue, put your head down and just deal with it-- you suffer stoically and attemp to pull yourself up by your boot straps. Your So auxiliary would still color that picture with longing for greater social connection and vocally bemoaning it's lack at times.
That said, I can become too inwardly focused to realize how sp-like I'm objectively being. This is because I have access to the feelings underneath and know the full extent of their storminess. When someone else says that they see me as unemotional or as being tougher than I experience myself inside, it catches me off guard. It's a little satisfying to tell that observer that they have
no idea. I'm just barely holding it back, they've never seen it pop out. Also, I will do a lot of things alone and cope with that as if it's the only option, later to be confused when others say they would never be able to do such a thing without help.
I have to clarify one thing, I do think its normal to be comfortable with some situations and not others. Especially for us as 4's, intimate interaction is so much more comfortable and filling than the greater social sea-- I would dare say that no 4 would prefer the shallow interaction of a crowd to a group of a few close friends (and find more comfort and freedom there).
This is where there's a countertype buffer. I'll pound into my head for years that I don't need connection, that I can and
must be able to survive on my own because it's my lot as an outsider etc etc core distortions, but in the end, what you say here is what's really true.

I hunger for intimacy no less than anyone.
Does that shed any light? Anyone else, feel free to chime in.
Your response was both insightful into the experiences I had in mind and consistent with what I've read - what very little there is to read - about the expression of sx-lastness in type 4.
