Reminds me of how YouTube's website doesn't let you full screen in Safari on the iPad but every other HTML 5 video is able to. And how YouTube throws a fit if you try and background it so that you'll buy "YouTube Red".
Somebody at YouTube has a hate on for iOS in general.
Background playback is a problem for YouTube because they pay for music licensing through ad revenue. I'm sure advertisers wouldn't be happy with people not seeing the ad they are paying for. With YouTube Red they have another revenue stream to pay for the music licensing. That's my theory, anyway.
Does YouTube actually pay for music licensing though? It's users are the ones that upload the music, afaik all YouTube is responsible for is responding to takedown requests
I wouldn't mind paying for YouTube Red, because despite all their issues, it is a great platform for content still (despite Google's greatest efforts to undo that). I also wouldn't mind doing that if actually kept their stuff up-to-date with the software and hardware of the device it's running on (in my case the 13" iPad Pro - where it took them like 8 months to add native resolution support).
Oh and the small little irrelevant detail that they don't let me: unfortunately I happen to live in Europe, so that means that I'm not allowed by Google to enjoy those features by giving them money.
Somebody at YouTube has a hate on for iOS in general.