And you're making it out like the Play Store is worth peanuts.
https://cybercrew.uk/software/app-store-vs-play-store/#h3
App Store led with an estimated revenue of $85.1 billion in 2021
Google Play Store generated revenues of nearly $47.9 billion in 2021.
Nobody's ever going to try something shady for "just" $47.9 billion :-)))
I don’t recall Facebook publicly throwing any tantrums over Play Store policy changes.
It’s also possible that being able to put a store on both platforms is the kind of thing that would get, say, Facebook to expand the Quest software store to mobile. They’ll want to do that for Apple’s headset at least, if these changes open that up to them—expanding that effort to include iOS and Android seems like something with decent odds of happening.
It still ended up going away and they gave up. So allowing sideloading is hardly the threat you think it is.