This is functionally similar to what Apple and Google do with their app stores. They don't explicitly ban certain devices, but they mandate minimum API targets, which means they stop allowing apps that support older OSes. This effectively blocks old devices as well once they stop getting OS updates.
This is part of the problem with walled gardens. There is inherently a conflict of interest when the same company operates the marketplace, creates the OS, and even sells devices that run that OS. If the marketplace were independent, they would not have the incentive to block new games for old devices.