What you are referring to is usually called “yield.” And, yes, ED increases yield substantially.
Yield is really the key independent variable in college admissions. Freshman class size is effectively a constant, at least at the level of selective colleges. The number of admission offers the college gives out is that constant divided by yield. The admission rate will be whatever that number is, divided by however many applications get submitted.
The more ED admissions a college makes, the fewer overall admissions it will need, since yield from ED admissions is always close to 100%, and yield from RD admissions is never close to 100%.
Overall, in recent years Penn seems to have accepted slightly more than 50% of its class ED. If that’s the case with Wharton, then an 80% overall yield means that it gets a 50% yield on students accepted RD. Which is great, by the way, for a school with ED. Sure, Harvard and Stanford get 80%+ yields without ED, but they have lots of applicants who would have been happy to apply ED if they could. The same would be true of Wharton. If all their ED acceptees were accepted RD instead, Wharton wouldn’t get 100% of them to enroll, but it would probably get more than the 50% rate it gets from applicants who didn’t apply ED.
Meanwhile, Harvard and Stanford likely get much higher yields from their SCEA acceptees – although not 100% – than they do from their RD acceptees. They don’t fill half of their classes from SCEA, either. They probably have something like a 90% SCEA yield and a 75% RD yield.