It could totally be thst apple made a mistake but since yours is the first post I see about it since the release of the phone (which I own Myself) I am inclined to think it is your fault and not the phone’s fault as I doubt the glass is any different from the 13 model. Very probably what happened is that you had a small rock or grain in between the wallet and phone, you maybe bended to grab something and the phone was pressed hard against the wallet, If there was something in between it could have made the glass crack because of the tension