Servers give priority to certain champions (or clients?) when calculating next move.

Kha'zix auto attack was faster than mine as calculated by when the animation started. This is also when brush should have been occluding its vision so that speeds up the possible speed even further. So these animations are actually slowing champions down as the server is telling the client to actuate the animation, but only completes the necessary damage step if the animation comes through correctly from the client. TL;DR this game is broke.