If u lean left or right the view is not perpendicular to the ground. This functions very well with the aimpoint. But if u switch to Telescopic sights the view is perpendicular to the ground again (the same feature like in ARMA 2).
IF you get prone and roll left or right, it is the same problem.
In my opinion this view should have an angle too, and when rolling you should "exit" sights. {F17340}
Dont really get the first part of the description but you should definitely break sight lock (scopes AND ironsights) when rolling around.
Just try it. Go into scopes and lean left or right. You will notice, that this view isn't rotating.
I think it was kept that way because you normally rotate the head along and the sights are not actually tilting for us, in reality.
It happens because the optics are a 2D image overlaying the players view as the FOV is modified to give the scope zoom. To rotate that 2D overlay as you lean is probably do-able but it's not that big of a deal..
I post here my related issue: When on lowest prone front stance, while you are sideways, if you zoom for scope view, the scope's view interface will not also be sideways.It will be horizontal...