It’s a catch-22

If you explicitly reference the horrors of Ben’s later actions it makes you wonder why he would exile himself rather than try to prevent it.

On the other hand…

If you don’t explicitly reference these events you might wonder what could possibly make him want to kill Leia’s son.

You could go with the implication that Luke is merely looking into Ben’s mind and doesn’t see anything of the future, but if this were the case Luke would surely see the light which defines Kylo’s struggle, just as he sensed the light within Vader.

I can’t see a way to navigate this act which remains legible with what we know of Luke from the OT.