@VeryLuckyParent - here’s the reason your argument does NOT make sense: Penn’s ED yield rate is about as high as you can get (98-99%). Even if you have a binding admissions agreement, AND you’re the most coveted school in the world, yield will never get to 100%. Some students decide to take gap years, others have unexpected events that compel time away, etc.
Penn’s ED yield is as high as it’ll ever be. Next year, with restrictive ED, Penn will probably lose some MIT or Chicago-caliber students in its ED pool, and the yield will probably be the same, for the reasons I describe above - the difficulty of getting 100% of 1250 students to attend.