i honestly have no idea. the reason it's back on my radar is apparently it's popular in asia right now, so the work i'm doing includes an MBTI score
but i agree with the principle of it, but it is a bit more fuzzy than the 16 possible values, probably it's most useful knowing your own so you know how to deal with the various conflicts. the first two letters are just positive if they match, the last two are negative if they conflict. at least that's how the evaluation algorithm i used says it.