Even without the “browser loophole”, developers are pushing Google and Apple about further permissions being granted and sideloading and whatnot. Apple and Google careth not… Your argument is pretty moot at this point.

No, not even without it. Without it there would be a significantly larger push. It wouldn’t just be a small movement. It’d be necessary. It’s like being on a computer and getting everything from the Microsoft store (if you’re on Windows). Sometimes they don’t have what you need, so basically every moderate user has had to download something elsewhere. It’d be the same on phones. Apple and Google would not be able to get away with preventing sideloading because every user and developer would care, not just the few of us there are now.