That isn't a bug. PiP is more accurate rendering to real life thus have a different perspective.When you look down a scope your world doesn't zoom in, just the area inside the scope. If you don't have a scope use only one of the eye pieces on a binoculor or a magnifying glass to test this out. Note the distance between you and the scope aka Eye Relief hasn't changed. PiP also lets you keep most of you perphial vision at the cost of performance.