I think this same issue was fixed in DayZ SA quite a while ago. Since it disappeared from "known issues" notes, solid objects like walls, and iirc trees and other objects as well, would limit the angle of lean you can perform towards them. Still works on doors, though, but that is very minor problem. In A3, though, you are able view through walls somewhat easily and reliably, which is a huge potential exploit. Kinda ruins the big improvement in A3, enterable buildings, too.
I'd say the problem is simply that the player character in first person, on game client, doesn't have a head model, although it does have a body model. No collider on the camera object either, so no collider to be blocked by the object like walls.
Whatever the issue, they already have a decent fix for it, as seen in DayZ. I'd say either they have some reason not to use it for A3, or then the person who reviewed this did so very carelessly. But they should definitely re-review this asap.