I have a broad social circle of many people- ENFJs, ESFPs, ESFJs, INFPs, INFJs, ESTPs, ISTJs, INTJs...
and the INTP is THE BEST at reading people. Without question. He understands people the quickest, knows their motivations, their weaknesses, their soft spots... he's absolutely amazing.
If that is the case, he's either exceptional for that type, or not an INTP. Empathy is not exactly an INTP strong suit, nor are the typological preferences which allow one to compensate for it to some extent present in an INTP.
That having been said, I know one ENTP who is very good at typing others, underlining that this is to some extent a learned skill.