It would be a, not sure what to call it, but a way to “connect” to TLJ making a connection about ‘the’ third lesson.
Of course the lessons back in TLJ was to disuade Rey from training as a Jedi, or “prove” the Jedi were wrong, but it would be a fun “twist” he plays on the lack of the third lesson (since Rey left) from the last movie and “converts it” to an actual “Jedi good/right” lesson.
Kinda would be a fun play on the whole lessons thing from the last movie.
Yeah, branching off of what Jar Jar said, if this became Luke’s “third lesson,” not only would it help to push Rey’s arc forward in this movie, but it would also act as a sort of epilogue to Luke’s arc in the last. He’s finally embraced the true meaning of being a Jedi. We’re not trying to stop the film from discussing fear, Hal - the lines about confronting fear are meaningful - we’re trying to find a way to make it more homogeneous with Luke’s story in TLJ. Luke was bitter in the last film; he should be a more positive force now, and not be dwelling on his old mistakes.
And the term you’re looking for, jarbear, is “through line”!
EDIT: Which deleted scene is it that Luke gave his Third Lesson?