You can not horizontally move the mouse & get 1:1 horizontal movement from reticle/crosshair on screen it moves in a curve across the screen, often dipping more to the left when moving left & rising higher when moving right.
If you try to correct for this & try keeping the crosshair moving in a level horizontal plane (X-axis) you will see the crosshair bobbing up & down (wavy)
The wonkeyness of this is even more pronounced when zoomed in & you move the mouse left to right several times.
And it seems that both standard aim & zoomed aim have negative acceleration.
Edit. I have tried both my Logitech mice & even clamped a straight edge onto my pc desk there is no 1.1 input the crosshair is all over the place.
How is this even so? How can mouse unput be so bad in a game in 2021?