Isn’t F-Droid an alternative store on my (non-rooted) Android device? I suppose it’s really “just an app” and that’s why I can’t update all my F-Droid apps at once? If that’s all true I think F-Droid might as well delete the “Update All” button, since it does not perform that function.
Perhaps F-Droid is assuming you’re on a rooted device with something like Magisk, but is that a majority of F-Droid users, or a minority of F-Droid users?
Everyone who cares about privacy, which are the majority of F-Droid users, avoid Google and to achieve that, they tend to install a custom ROM with no Google footprint, like LineageOS. To be able to do this, they need an unlocked bootloader and so they can install F-Droid Privileged Extension from there. No need to be root actually.
F-Droid can’t actually update the apps in the background without the privilege extension. You need to confirm every app change that’s not from google playstore, if you’re using stock android.