Website
It's a bit edge case, if you already have videos in the playlist that are released it seems ok - but only the released videos are displayed in the playlist (and counted in the totals), it's just if a video in the upcoming section is added to an empty playlist, then it'll disappear.
Or if your watch later playlist is empty - you can add stuff to that even if it's disappeared though using the extra icon on the vids, and it pops back into the playlists list again.
So I can't create a playlist of "coming soon watch later" vids essentially.
I've just checked the app for you as well (Quest 3), and the playlists missing on the website are shown in the "My Library" section, but if you click on the ones with only the Upcoming videos in them, it shows "No Videos Found, Try changing search conditions"
