I think another reason this approach works well is because it stills leaves the question open regarding if she would be able to beat Kylo without tapping into the dark side. So for people who ask, “Where is the tension with their duel in IX if Rey already beat Kylo in VII?”, I think it helps address that issue.

Though to be fair, when Vader and Luke had a rematch in ROTJ, did anyone really ask, “Where is the tension in Return if Vader already beat Luke in Empire?” I know the situations were different, but just because Fighter A defeated Fighter B in their first match, that doesn’t mean Fighter A will win every time they have a rematch. That’s what makes rematches fun to watch. Maybe it is just weird to us because we’re used to the formula of the hero losing the first fight, THEN winning the last fight. Since we know that formula, I think that is why some people feel the outcome is predictable, but adding the idea that Rey won their first duel by using the dark side helps makes their rematch more interesting because we know, as a Jedi, she has to beat him without it now.

Regardless, the theatrical film already gives off the vibe that Rey is pretty angry when she knocks Kylo down, so you might as well lean into that and demonstrate how the dark side is the “quick and easy path”, which is exactly how a lot of Rey critics would describe her capabilities.