I disagree with your typing of Andrew Wiggin.
Andrew does seem to be self contained, but that is true of many INFJ's as well. INFJ's who have a Ni-Fe dominance, and who are further along in their development of their tertiary Ti function, possess a very heightened level of control over their emotions. I've never known an INFJ (although I've only known a few beside myself) who are not, at least partially, self contained. INFJ's are just as sensitive as INFP's, we just tend to absorb more emotion than we give off. Extroverted feeling means we absorb emotional energy, recharge off of it, from the outside; we also tend to give off emotion, but it is quite easy to take that extroverted energy, and filter it through our Ti function to soften, if not completely suppress, our true feelings. If we don't want you to know how we really feel (and we wouldn't in a competitive atmosphere like the military, or specifically battle school) we won't let you in. You can still see basic emotions and feelings, like fatigue and aloofness, but you aren't going to know our true feeling on the subject unless we trust you and let you in (like when Ender cried in front of Bean, and later his Jeesh on Eros).
In reading the book, you get a feel for how Ender thinks, and he is most certainly people oriented. I mean he's a great commander, not because he has a complete strategy, but because he knows his commanders and his subordinates; he understands their strengths, their weaknesses, and how to keep an adaptive strategy. He empathizes with people and understands them too deeply, too wholly to be a T type. He seems to be using Ni-Fe, then Fe-Ti to make his decisions. Taking guidance from his intuitions, applying them in the emotional and psychological context of his opponent's mind (empathy), and then takes what he expects his opponent to do, and thinks of a quick strategy to counter. Those are the steps that I saw in his thinking. Had he been an INTJ (like Bean), he would have first translated his intuition into strategy, then applied his strategy to his opponent, to see how he would then react.
Ender uses deep empathy first, in order to understand his opponent's motives. Once he understands how his opponent thinks, what drive them, what their likely strategy is going to be, he not only understands what his opponent is likely to do, but where his enemy has left himself most vulnerable. The only other person who understands where he has left himself weakened is the enemy himself, if he even is conscious of it (like Bonzo).
I must admit, I am a bit bias on this. I myself am an INFJ with a well developed Ti function. I believe Andrew Wiggin is the same, not because I want him to be an INFJ, but because in reading the books, I identified with Ender's way of thinking at the deepest level. It was like reading about myself had I been in a situation like battle school; maybe it was Card doing a great job with his characterization, but I still stand by my position. Wiggin is an INFJ.