This isn't even exclusive to M+kb. On top of that, I'm pretty sure KB+M players can't even do this if they're on legacy (not 100% sure on this though); this effect is caused by how the player rotation is matched to always face the camera in Standard whenever a camera movement occurs. Gamepad players can do the exact same thing by using standard and wiggling the right control stick left and right rapidly, since it emulates the 'do GCD, camera movement causes character rotation to instantly snap them away from looking at boss' effect.

Now, it is very cumbersome to do on controller since you need some good finger acrobatics to do it, or some people might dislike playing on standard, but the point is its possible.