I saw a system of that kind here first, where each type breaks into a subset of four, forming 64 in all. It's a very interesting approach, so I do hope more data is assembled in order to better test the underlying theory. As vultology focuses on eye movements and microexpressions, it circumvents interpretive uncertainties relating to thoughts, statements, values, and so on.
It is not a theory. It is how somebody use his function. Thing that somebody use Ni and Te function it doesn't mean that he is INTJ. Somebody instead 2nd function can use 3rd function and each of function can be overused.

What a mystifying moniker, "true INFP." What does it entail?

That type would be the least likely alternative. Beyond their lack of extraversion, I have noticed that INTJs struggle to harmonize thought and expression. Furthermore, whereas I value exactitude, INTJs consistently misuse words and shoehorn concepts, and thereby often run the risk of pushing conversations into their own private universe. This is very far from my approach, not to mention my occasionally florid style in speech and writing.
"extroverted" (with "" ) means social since as you know extroversion on function is not same thing as being social! But INTJ-T1 are very very "introvered" so nope for you.