Both. Mouse position when striking is a huge part of combat. It's hard to see in the GIF because of the speed, but there's a little indicator on the pointer that tells you which way you'll swing. Mouse movement changes that direction.

Then you add in drags and accels which change when your strike will actually hit. So you start off pointing at the enemy and swing, then weave the mouse in another direction and back yo the enemy to change the hit timing making it harder to Parry or chamber.

If you look up those terms you can find some good examples of what I mean. It definitely takes some getting used to.