What about one family PC with three accounts, is the game only playable on one account?
E.g. Dad buys a game, ostensibly for the whole family (we don't know if Dad really is fooling himself on this) and it ends up on Dad's Microsoft account.
If another member wants to play, does he/she need to log in as Dad? And see the mess of private documents/desktop icons, email notifications not intended for him/her, and such.
I'm asking a candid question again, just because Windows has been the traditional local computing platform like we did in the 80s and 90s, till now. So seeing the store/account built right into Windows brings questions as to how this works. If you get a "traditional" game version that installs system-wide for everyone and the redeemed account version is an additional thing, fine. If you get an "account version" or an Xbox version, I have to wonder. Although family sharing is something that the store can implement (Steam has done for a couple years?)