hey! nah, it's not really native ports in the way you might be thinking. microsoft has official backwards compatibility for a ton of 360 games on series x/s, but it's done through their own emulator layer. so while it's official and works great on console, it's technically still emulation. xenia is a totally separate, unofficial pc emulator project. both are emulators but one's official console support and the other is fan-made pc stuff. makes sense?
