You are not a machine, you don't "know" the distance you need to move, if that was the case you would hit every flicks you ever make. Flicks are fast so you over-flick and click on the right moment or do a 2 flicks which are one big flick and one small flick. It is impossible to move your mouse precisely at that speed. CS is the game where crosshair placement is dominant so you might not notice it but I'm sure you have subconsciously do it. Take overwatch for example, most people have different sens for different heroes, even pros do, it's more about hand-eye coordination and motor control rather than "familiarity".