Ok, so now I now better where @kouhai stands

I think Socionics clearly shows that they have in fact found the real types. The 16 types of IM. The amazingly accurate structure of intertype relationships, model A etc. shows this. I mean it is a practical matter of confirming this that one can do and has been done.

So Socionics is not just a matter of "interpretation". It reveals a very fundamental structure in the mind that shows itself everywhere.

What is then Jung? Obviously he had also seen the same phenomenon, at least in part, anything else would be absurd to assume. The question is how accurate he could describe this. From what I've read he seems to be talking about the same types as Socionics, but he is more of a phenomenologist who is interested in very precise descriptions of psychic content. For example, when reading Jung on Si, I can totally relate this to Socionics Si.

Definitions and descriptions can deviate from each other but still refer to the same phenomenon, so I am not too picky when reading Jung.

MBTI is more problematic. They too are talking about the same types, at least in principle. A quick look at the type descriptions shows this. But the analysis of functions is too different from Socionics, and they seem incompatible. Because MBTI doesn't understand the type relationships, they lack additional data that is needed in order to get the types right.