YouTube has started to gate higher bitrate videos behind YT Premium

To see the case in point, this is a generic fractal zoom video.

Go to the gear at the bottom of the video, and change bitrate. There is now a "1080p premium HD, enhanced bitrate". This setting is gated behind Youtube Premium.

I've never seen this before. And it goes to show that I could easily see this becoming a thing for many other videos as well, and possibly even all 1080p videos. Again, this is conjecture from limited data points.