While the music plays the Android lockscreen is set to some random scene from the video. It's not always a good look.
Is there a way to prevent the lock screen set by YouTube Red?
Edit: Android 8.1.0
It appears to be a standard Android feature. All my music and video apps use it.
I haven't been able to stop it by blocking all notifications, by blocking the app notifications, by setting the lock screen wall paper, and so on. The only option that I haven't tried is to stop using Google Smart Lock as there is a possibility that it is involved.
The YouTube app allows me to turn on the Restricted video setting but as I don't usually play strike such videos I've never had any blocked.