I think it's true...
I'm definately not a social butterfly, a few good friends suffice...
However, both my ISTJ boyfriend and ISTJ sister are definately more anti social! I think it's because INTPs enjoy discussing theories with people close to them whereas an ISTJ is more structured and purposeful in nature. It's not to say that neither of them have friends nor that they do not go out with them...it just happens very rarely.
It's one of the things I like about my boyfriend, it means I don't have to go out all the time either! I'm quite socially awkward

lol I only really come out of my shell in one on one conversations with friends. ISTJ's overly organised nature can be a bit scary though! It's also no fun talking to them about abstract things, you can almost see suggested theories fly over their head as they switch off or think about a more efficient way of organising their sock draws :tongue: