I am the same way with most people I know, minus one or two people. As for the "He has many acquaintances, but claims to have no one he is extremely close to" bit, I relate to this as well. I don't have any trouble getting to know people that I have to, but I don't consider those people to be my friends, and thus feel little need to communicate with them outside of settings where it is necessary/for my own benefit.

From the few things you've said, it is possible he is INTP, but it may very well just be that he is stressed out or busy.