Yeah, Jung basically said in his book Psychological Types (where all this Myers-Briggs stuff evolved from) that he was an introverted thinking type with auxiliary intuition of some sort.
But, apparently he has also stated other things in other places. Kind of vague.
He definitely had very strong Ti. And an INFJ with strong Ti can easily think they are (and test as) an INTP or INTJ.
Also, due to the nature of the tertiary function (which Jung didn’t come up with), it has become evident that any given Myers-Briggs type can fall in love with the cognitive function at the tertiary. It is what I would term “very classical” in my observations of MB types. Like, it’s so “classic” when I meet an INFJ that is very Ti. It’s like “by the way did you know that I like Ti? I’m very Ti, ya know. Ti, Ti, Ti!” etc.
The tertiary is the one function that is what I would call “a pseudo-self-identification function”, whereas, the dominant function is the “self-identification function” proper.
It’s classic. One of the most helpful ways to identify who is what type is to look for that characteristic pulling towards the tertiary function. Assuming that is going on in some degree, it is very telling. It is like a person that is playing poker who gives away their hand, or something like that.
Guy in the picture? I see Te, not Se. And I see thinking over feeling. Looks more ISTJ than ISTP. I see Si-Ne axis over Se-Ni axis, so if he is intuitive of some sort, he would be more Ne than Ni. And probaly not a dominant intuitive, so Ne in the aux. perhaps. I see J over P in his projection. There is a closed look in his eyes and they are radiating a sort of “I know better than you” arrogance. Not a guy who is going to be too open to input from most people whom he probaly considers to be beneath his station in learnedness or practical experience. He has the look of some one who takes pride in some kind of small knowledge that he possesses and is not aware of the bigger picture too much. I see Ne echoing (inferior position).
Yeah, ISTJ is what my first impression is. Runners up: INTP, and yes, maybe ISTP a little more distantly. He looks Te aux. though. I think that is the projection of hardness you are seeing that you are associating with Se. But, Se aux. projection looks more like Eminem or something. It’s more sexy and dangerous in a visceral way. I don’t feel that from this guy. I feel a projection of “competence”. That’s more Te.