I can't believe Google hasn't yet implemented 60 fps for the Android TV YouTube app, while my phone has it and something like the Twitch app had it from the beginning. I sideloaded from apkmirror the mobile YouTube app (320 dpi version) today and unfortunately it seems to not recognize the Shield resolution and it's limited to 720p 60fps. Let's hope they will implement it soon on our wall powered tv boxes connected to giant screens...
Yep they should update it but you can cast the 1080p 60fps videos to the Shield