It can't be too hard to manage well. The backend positioning notifications and the time either side of the notch is handled by the manufacturer, so they can control when it shows and when it doesn't.
- If an app knows how to handle a notch (read: plays nice with the manufacturers notch API), great
- If an app in portrait mode can't handle a notch, then just leave notifications up
- ditto for landscape, just turn the bits either side of the notch black (or whatever colour the remains of the bezels are) so they don't stick out
For portrait apps that can't handle the notch, you've kept the status bar on top of the screen and freed up a bit of vertical height for more content. If it's a full screen video, you're basically notchless (couple mW to run the extra screen area, no big deal)