Way to allow site do something on user action (full screen, for example) is good, but some broken site can use privileges without full agree of user. For example, start playing audio or switch window to full screen.
In my opinion, when sites do something request user action or privileges, browser should show message with button to ensure page would never do this (dropping privileges of site).
For example: page asks to allow display notifications in notification are of user. User click never, but page grant right to do so. So what… ? Browser (when my change was done) will display message what happens with button to drop this privilege and ensure page never get it itself.