

It's similar to Nvidia's announcement last week that some GeForce Now games (starting with God of War) you've begun while they were supported by the service will remain available when the licensing term ends. Game churn on XGPU is pretty low, so either Microsoft expects it to increase or that the capability is purposefully limited.

So really, it means that in the beginning, the feature will only be useful for games that have left the service and that you've bought from the Microsoft Store - because the service doesn't support other game stores, like Steam, and only carries over progress and achievements for its own Store-bought games.
