Can categorically state the phone hasn't been dropped or had any impact. There was a crack in that ring for many weeks and a couple of weeks ago the crack opened up. Again, there was no impact causing the original crack. We both have the same case and hence able to compare.
By the way what you seem to refer to as a scuff? is not a scuff - it's the unfinished edge on the camera opening. We went ahead and peeled away the remaining part of that ring, and the whole camera opening is not a perfect cut, its a jagged edge.... as we're not supposed to see that edge due to the fixing of the ring. Like, done by hand or jigsaw (as opposed to laser or similar).
EDIT: in a funny turn of events my wife prefers the case without the ring now.... as it lays completed flat on a surface and doesn't have the 'rocking motion'. Camera lens remains protected.