'PC & Xbox' shouldn't imo be given the word 'exclusive'. If it was 'Windows Store & Xbox' then I can see the 'exclusive' card used because Microsoft owns both and keeps their portion of each game sold. But I could use Windows 10 as the OS but a different service for games (GoG, Steam, etc.) where Steam, GoG, etc. own those digital stores and I believe keep all the revenue not distributed to the games developer/publisher.
Most if not all popular games except for a few GoW/Forza/Halo are available on Steam. I've not bought any games from Windows Store since its inception.