How is it unethical?
Because on the one hand you'll have people who are actually trying to improve their skills and want to learn how to take turns properly, people who'll earning their way through the game. Then on the other hand you'll have people who will get by by rewinding and rewinding and rewinding.
I think it creates a bit of an imbalance, people who will rewind for the purpose of learning the corner and then people who will rewind just to do it.
But I mean, me arguing this is kind of silly, because its just a game and who ever owns the game can do whatever they like. I just think it will promote an attitude of rewinding to get ahead rather than rewinding to learn the right way to get around a corner as fast and as clealy as possible.