It’s not the movies fault that you missed an important detail.
I missed it cause it isn’t there.
Uhh, what?
the important detail(s) explaining what Luke was doing and whatnot. It wasn’t there.
It was clearly shown that he did not interact with the salt.
EDIT: Not sure about the image policy, so I’ll just put them in quotes and pretend that it makes a difference.
Kylo:
Luke:
Maybe some people are super duper observant, but that’s a detail which I doubt many people noticed. And frankly, it isn’t an important detail. It was a nice touch but that’s it.