Note that I said LIBERAL application. And my biggest problem with it is when it's used too heavily in younger people rather than older people. I'm also more wary of people using the Inferior to explain behavior than I am of them using the Tertiary. It's just that occasionally, people use it to dismiss really huge patterns in behavior, which sends up a red flag in my mind.I disagree a bit here. Especially as one gets older, the tertiary and inferior become important. All of the conscious issues with the dominant and auxiliary have been addressed, so the mind begins to explore other means of understanding. Overall, I find it rather useful to spot modes typical of a function in tertiary or auxiliary position: e.g., if one sees "tertiary Ti" in an "INTJ", perhaps they're INFJ without the "touchy feely" behaviors, or "tertiary Fi" in an "INFJ" indicates the reverse.
I agree that one shouldn't use tertiary or inferior to "explain away" mistyping, which is simply an example of your #1 item.
Paying attention to how the function might manifest in a tertiary/inferior role would be a GOOD use, I just don't like it when people just see a function, and decide it must be tertiary or inferior so that it will fit the current pattern, without considering that the way they're using it might be indicative of having it in a higher position.