Some links would be helpful to make clear we are talking about the same thing. But from what I have found that happens after people use their drone, which means they have already left their body. If the bug is showing the first person animations though you can see a ton of head movement going on which is clearly not reproduced by the camera when you actually are in first person, so they aren’t copying the head position exactly with their camera.
Also in rainbow six, your own character doesn’t seem to cast any shadow in first person, which is a strong indicator that the mesh and animations get changed when that bug happens.