YouTube has developed a panel of controls that come into effect when it is being used on a smart TV or Chromecast-enabled device. Now, it may have also added voice commands and new remote-style buttons in this menu. They have been reported as existing in a server-side update thus far.
https://www.notebookcheck.net/YouTube-on-smart-TVs-to-gain-voice-control-support.448208.0.html