In my cases, the filter remained intact and no pieces came out til I removed it from the lens. So that premise is just part of a lot of speculation. My impacts have come from leaning over and the lens swinging into something. I have a 400mm 2.8 that accepts the clear or polarizing filter near the back of the lens And the front element is huge. I don't expect the filter to be bullet proof, but in my case, neither the object nor any glass got back to the front element and went no further than the filter. Since there was enough force to shatter the filter, it is logical that that is enough force to scratch the front element even if it doesn't break it. I shoot a 46 mp camera, and don't want a scratch on the front element to degrade my image or reduce the value of my lens.