The difference is that Google’s sideloading experience is intentionally full of warnings and hurdles. Do you really think that if Apple had a court ruling against them they could get away with that? No, Epic (et al) will be very clear about third party stores being utterly seamless to install and use.
That’s why we’d see a proliferation of stores on iOS.
So now you want third party app stores and no warnings? Even though Epic - one of the first major apps to try side loading, actually had a security vulnerability.
Ew, god no. I think Apple should be allowed to offer us their idea of a good product and let the marketplace choose between that, Google Android, or other competitors who believe they could do better offering open source Android. The idea of having parts of your product designed by the competitors who envy your success is utter madness.
That’s why we’d see a proliferation of stores on iOS.