I’m trying to wrap my head around the fact that they are having a huge argument about something that the OP should only be minimally involved in. The essays belong to your son. If he asks your advice then give it. If he asks you to review, then do it. But ultimately it is his application, his essay, his decision. If he ignores your advice and doesn’t get accepted (which may have nothing to do with his supplemental essays) then it’s on him. Why are you so invested in this as to have a “huge argument” over a supplemental essay?