It’s a decent idea Starkiller, but I would say it doesn’t work fully because with a proper understanding of the force, we know that the future is always in motion. For Luke to have such confidence in Kylo’s future violates a very foundational aspect of what we know of the force, and I think this dialogue reads as Luke simply acting like an arrogant dolt who doesn’t understand how the force works rather than him being forced into a legitimate moral dilemma.

Him just saying that he knows Ben’s fate is sealed comes off as him being in great error about reading the force vision, which Rey immediately corrects and she seems in the right. I don’t think this fully solves the problem of Luke still being presented out of character.