Well it's not what I am saying. And I agree with your response. I train in Aim Trainers for getting better in the game I main.
Let's say that I main Battlefield.
I will use in the aim trainer the sensitivity settings just as I use in game (Also same FOV, Co efficient) .
and yes what I use in the game is changing. For COD for example, since I snipe a lot (Quick scopes etc.) I had to get my sensitivity up , and trade for less accuracy for sniping, just for me to get quick movement. I raised my sensitivity up until it wasn't comfortable to snipe and got used to it.
Than I can train in my aim trainer effectively. The drills that I do can translate to the game.