Well, the false-positive rate for people claiming to be time travelers will have been pretty high, if we are going to have been honest. At least in the reverse direction.
I’ll also have concluded that the verb tenses will have been miserable. We will have needed a less cumbersome language. Maybe I’ll have solved that, someday.
I mean try untangling ‘You will have had to have had had had traveled’. Bit of a pain to discuss iterations of a loop, and that’s not even that many deep.