I’d rely on what the AO told you. But it does make sense that Penn would operate that way.
Penn has a very broad definition of legacy --parents and grandparents count. And any kind of Penn degree counts – undergrad, JD, MBA, MD, masters, PhD. Compare Harvard where you’re only a legacy if a parent has a Harvard College undergrad degree.
Also Penn is a big ED school and Penn tells you to apply ED if you want the legacy tip. So Penn pretty explicitly operates legacy admissions as an adjunct to its size-able ED program. And interest/donations wouldn’t be relevant for most ED applicants.
Gtown operates very differently. No ED, just REA. Gtown continues to use its own application – maybe the only top school left that does not permit the Common App. Gtown intentionally makes it hard to apply. So the whole drift of Gtown admissions is to focus on kids who really know, get and want what Gtown offers. Given all that, no surprise that they would value involved alumni more when it comes to legacy admissions.
But don’t overthink it. It is impossible to gauge exactly how much boost a legacy application would make for you at either school. Since the combination of the ED/REA rules makes you pick a primary target, go with the one you like the most.