"This week on the Game With… stream, you can play Overwatch with Senior Creative Director Joe Staten!"

"Here’s what you’ll need to do:

Make sure Overwatch is up-to-date on your console with the latest update,
Friend Joe on Xbox Live (gamertag: deckard),
Load up the game and be ready to play this Wednesday, August 10th at 11am PDT!"

Link:
https://www.microsoftstudios.com/news/2016/08/10/game-with-senior-creative-director-joe-staten-august-10th/

Heh, I can understand why they might want to avoid using a Bungie-made game for this, but I figured they would at least use a MS first-party game (since AFAIK Joe has nothing to do with Overwatch). I guess Joe just picked something he's been playing lately. :)