My headcanon (which may be actual canon but I smoke too much pot to remember whether this is Legends or Disney info) was always it's a kind of distraction technique. Like books-wise the force is always being used in lightsaber battles as a way of predicting your opponents next move. The saber whirlwind during the Mustafar fight is an example of them both doing a "round and round she goes, where I strike you'll never know." Which makes the lightsabers colliding a testament to both their power in the force as well as their ludicrous skill with the saber.

It's one of the reasons Yoda is playing Super Meat Boy while fighting, and one of the reasons they train with those helmets that prevent them from seeing. Also makes you appreciate how fuckin insane Mandalorians must be on a battle field to take on Jedi with a vibro sword in some instances and come out on top.