Video evidence: https://www.youtube.com/watch?v=9KpkdCIfJ-8
You have to actually be looking through the binoculars in order for this to happen. Simply having the binoculars in your hands when switching to your weapon doesn't cause this bug. This also occurs when using variants like the laser designators or range finders. It also doesn't seem to matter what weapon you're using or what gamemode you're playing.
I don't know if this behavior is intentional, or simply an overlooked bug, but I thought I'd report it anyway to make sure. If this is intentional, then I suggest that this be changed. I know I'm not the only one who finds this behavior to be a minor annoyance.