It also just kinda harshes everyone's vibe when they eventually realize they're being gypped and paying a lot more than others for the same thing, and that can cause people to just unsubscribe.
According to App Store rules, you're not allowed to disclose the App Store fee to users. So Patreon is not allowed to explain to users that 30% is going to Apple, nor to explain that there are other options. I'm not sure if Apple regulates messaging to creators as well.
It's too big of a decision to take without actual numbers, and having gone through it for a few months also helps on the communication side: on the surface Patreon at least gave it a try, and there's even a chance users are pissed off enough by the new model to campaign for that change and defend the move to their fans.
Or, of course, eating the 30% fee yourself deincentivizes you to use the platform (or upload content as regularly) if you opt for that one
I'd say it's a loss for everyone involved except for Apple. Since Apple now gets a cut from all transactions its hard for me to see this as anything else except hostile and arrogant