I thought it was a bug, but then I realised this is a thing youtube are doing and it's fucking awful.
Edit: double checked and because they moved the layout the Unhook extension isn't working properly anymore to hide this obnoxious crap :(
Edit 2: That's hilarious, they seem to have borked the whole site at least for me with this change.
I haven't been hit, yet.
Google knows I disable every new feature they throw at me, so they don't bother testing things on me anymore. I'll get hit when it's fully rolled out.