I don't get it
Why not just reserve the left/right area in the notch for status information and leave that there all the time? It wouldn't be useful for a web site to display "full screen" in that area anyway, so why account for it at all? The web page should be below it. Honestly I'd prefer not ever having a true "full screen" and always having the time displayed.
I can't see them having much luck getting web designers to account for that, at least not for a few years until Apple can get up to a quarter billion or so 'notched' phones in circulation and they're harder to ignore.