This might not be right for Legendary, but maybe a future edit could imply that somehow in one of the flashbacks.
Maybe when Ben uses the force to collapse the hut and it cuts to black, we could hear a few brief lines of overlapping dialogue from the other students arguing/fighting.

“He killed Master Luke!”

“Luke attacked him!”

“Murderer!”

“Traitor!”

“No!”

lightsaber ignites

Then it cuts back and Luke sees the aftermath.

Also, Nev had the idea of replacing Ben’s blue saber in the flashback with Anakin’s saber, which I think would fit pretty well with the idea of the KoR being Luke’s students. Maybe kyber crystals and lightsabers were really hard to find by the time Luke started training students, so none of his students ever built one. That’s why the KoR don’t use them. And maybe Kylo finally tried to build one, which explains the rough construction of his crossguard lightsaber.

I like the Craster’s Keep comparison. I never made that connection but I picture something like that too. Maybe sides were being formed way before that night, but when it finally happened, people had to choose sides quickly and then all hell broke loose.

Anyway, I still think Hal’s dialogue change is a valid way to go with it. It simplifies things. Raises less questions. It would be interesting if we could somehow imply Ben was defending himself, but I also don’t think Ben really cares to try and justify his actions to anyone at this point.