That’s really interesting, and a little hard to explain. Brown used to be the only college that did that, as far as I was aware, and it abandoned that rule 6-7 years ago.
Penn’s rule may affect Chicago EA applications some, but it will likely affect Penn ED applications more, in a negative way. I wonder why Penn made that change. It doesn’t make any sense to me – the rule was always that an ED acceptance trumped EA no matter what. And Penn allows simultaneous rolling admissions applications to public universities, which is especially important because three major in-state alternatives for its core markets, Pitt,Temple, and Rutgers, all have rolling admissions. So a candidate turning down a Penn ED acceptance on financial grounds can have a definite alternative to compare with Penn’s offer. Avoiding that is pretty much the only argument in favor of Penn’s new rule.