sometimes you can have a youtube video that is paused, and you hit play/pause button thinking it will unpause it but for whatever reason that video seems to not be registering as being unpausable so OSX thinks there is nothing to unpause, so it opens itunes, it's one of the reasons apple was cited under geneva convention violations for unusual weaponry last year
Mainly want that button for pausing a video to play music or vice versa. Don’t love the logic (which will it play, or pause?) but maybe it’s about as good as it could be without more complexity like first press pauses background playback, second press begins foreground playback. (Could probably script that now that I say it, an easy Hammerspoon or something.)