So thats the invisible "wall" that I was hitting while aiming. I did feel that invisible barrier multiple times while aiming, especially noticeable in CQ fights when firing from the hip when you and the enemy both move at the same time or jump etc.
Didnt bother looking closer into it, but now after trying it in a custom game, it is indeed as described in the first post.
The screen even goes from smooth circle rotation to jittering once you hit the invisible barrier.
If anyone bothers, you could try creating a reddit post about it or tweeting an image of this to vonderhaar, mattks or alexconserva and ask them to fix it. I however dont really enjoy the game, so couldnt care less about this. Id say this is like the biggest non-issue in the game right now, compared to all other major issues.
This deadzone limitation does really suck dont get me wrong, but again- thats the smallest thing to worry about right now with how much stuff is broken/overpowered/etc., sadly.