I don't think this properly describes the situation. If this goes through, Facebook doesn't have to "bake into their service is a fallback for when a user doesn

I don't think this properly describes the situation. If this goes through, Facebook doesn't have to "bake into their service is a fallback for when a user doesn't give them permission", they can just make sites require this permission. If the user declines, the site won't load. Alternatively, the do what you're suggesting, but the site gets no revenue for that user, this will pressure the sites to continually ask for the user to re-enable the permission or change the way the notice shows up so that they eventually accidentally allow it. Either way, nothing will change.