This looks like a dupe of  Issue 654140  which had a lot of discussion about this and a fix for the ability of a site to use the Esc gesture to get back into Fullscreen.

The bug was that while the Esc keydown event was suppressed (and therefore ineligible to trigger fullscreen), the keyup event was not. foolip@ fixed it so the corresponding keyup would also be suppressed. In ~M56. Is this still an issue today?

We might want to be more aggressive and put a timer on re-entering fullscreen (like 5 seconds) so the user always has an opportunity to close the tab.

I think if the gesture thing is fixed we should just close this.