It's like people forget cross-buy's been a thing for years.
Smart delivery is not just cross-buy. Xbox has also had cross buy for years with Play Anywhere.
It seems like part of Smart buy does have something to do with entitlements, but more so with delivery/packaging of the game itself. "
Fast Start" seemed like the beginning, and now Smart delivery is the next step.
I would expect this is part of Microsoft's "
GameCore OS" which is supposed to make it easier for developers to support multiple platforms with a single game package. Gamecore is part of Microsoft's broader
Windows Core OS. If my prediction is true, it'd mean that games that run on Gamecore would be a single store sku. Whereas games that don't support it may feature distinct last gen / next gen versions, where access depends on how the games publisher has established entitlements.
Maybe
tomwarren knows something about this?