Of course, this makes "the meaning was imparted originally, rather than being chosen post-hoc" into an unfalsifiable position.

So, I can imagine a scenario where Yoda says cryptic statement X, and then privately expands on X to make it specific in a letter, and then a month later the person says "I finally get X," and then Yoda's letter is opened and checked. That is, Yoda could know exactly what path the student will go down in response to the cryptic statement, and we could test that ahead of time by showing Yoda lots of students and getting him to write down lots of predictions.

But you're correct that Yoda could inflate his statistics by saying one common deep thing, and then when students come back with twenty specific epiphanies, saying "yes, that specific epiphany was caused by my deep statement," even though he doesn't have the ability to predict which student will have which epiphany. (Especially when it comes to reading ancient works, we only have our retrospective predictions and judgments!)