Yea I completely agree with that. They just use what "feels good". Actually I can perform extremely well but only under the right conditions.
When I started playing CSGO I managed to find my sensitivity easily, I remember I didn't even know any advanced stuff or strategy about the game at the time, but still I managed to get global just cause my aiming was way better than the other people.
Reaction time is everything, and the "first shot" is the most important in my opinion and I agree with that as well. In games like Battlefield it's not even that important considering the enemies are often kinda bad honestly, in skilled games first shot is crucial.