That only launches the game through the correct store. If the game doesn't implement cross play, you can't play together.
> They also support voice chat for groups and players not in game.
But you're trying to be in game with the person, and again if the game doesn't do in-game voice chat, you have to find alternatives. On a console you join a party and the software correctly handles the cases around "do I want to put you in a voice chat channel for your game" (because it has to to pass certification).
> File a bug report? Or you just came up with some hypothetical issues?
Really helpfully closed after 30 days of inactivity. https://github.com/docker/for-win/issues/42. (I didn't make this bug, but I found it, and just logged onto my xbox instead).