> > > a page needs to know how to avoid the rounded corners and notch at the top or side of the screen
> > Why would Apple deem it OK to place this burden on web developers?
> We're not requiring them to do this. By default we'll avoid the notch by insetting everything. However, if the author wants their page to use the full area, they can opt in but then need to avoid the corners.
Remember that the iPhone X has a screen with rounded corners. Maybe it's not the only non rectangular screen out there (I guess that some watches have round screens.)
There even is a CSS draft for round displays: https://www.w3.org/TR/css-round-display-1/