The issue is there are people playing with USA ON (as they should do) but saying there were issues with the mouse input and acceleration, and controller settings affecting input, when there wasn't ever. This isn't helpful, you don't have mouse accel appear out of nowhere unless it's packet loss, as you'd have to write a math function to do it. People end up wasting their time fixing a problem that doesn't even exist, and wasting devs time investigation stuff that doesn't need to be investigated, when lets face it - they have a whole shit ton of other stuff to do to fix this game.
The race condition / packet loss issue you observed in the beta was 100% fixed before launch.
Whenever a new shooter game comes out, the one thing you can always guarantee is "Sens feels off", and loads of snake oil "fixes" appearing on Youtube which are just a metaphor for "I haven't learned how to play the new game yet so am looking for something to blame as the erroneous factor absolutely CANNOT be me!"
There isn't even any "issue" with USA Off as far as the mouse input per se - it was requested by a designer to be the same sensitivity and not to scale like USA does. The engineer did what he was asked. You could still use the sens sliders to scale the sens to anything you wanted so nothing was ever "broken". This is obviously just a design choice - admittedly one that makes no sense, but there you go. I will ask again to see what the change is they mention (if it's anything at all) but I would also conclude the designer just realised the request was wack and they are putting it back to how BFV worked when USA is Off (which given that is just USA ON with no coefficient selection and therefore a totally redundant feature like it always was it should not even be in the game in the first place).