Perhaps I'm wrong but couldn't intertype relations be used to statistically prove one's type?
For example a person says they're, I dunno, type X. If there is an informational metabolism, and it is fixed, then over time, as that person interacts with other people intertype relations will emerge. And you wouldn't need to know much about either those other people or the relations themselves. The other person could be just an irrational type. And the relation could be just of occasional miscomprehension. Given enough of these bits and pieces one could build up a picture of the original person's type. Consensus and the person's personal opinions aside. Question mark.