I have a pair of Avantree Operas attached to my Sony Z9F TV, and they work great. They attach to the optical port on the TV which is always active. Not sure all TV's have this ability though ...
I believe they are referring to connecting blue tooth to the Xi6/XiOne boxes.
Probably, and the option suggested by @reed935 may not work for some people as he mentioned. Not only may the TV not have an optical output, but that optical output may not be active all the time, meaning you need to go into the TV's audio menu and turn on "external speakers" or similar option limiting the audio to the headphone wearer only.
One option that may work is to purchase an Audio Video Receiver, that allows for HDMI or Optical input connection with a set of speakers and an optical or analogue audio output connection for a set of headphones, or a headphone jack. (Headphone jacks usually turn off the external speakers on an AVR.)
Just to follow up a bit, the Opera headphones also support other connections as well, like Bluetooth, AUX, etc. Since the Xi6 is sending info to the TV, having the headphones attached to the TV is no different then to the Xi6 box itself, as far as I know.