Is Xbox considered Windows?

I have a simple question, maybe someone here knows the answer.

Ikinema Runtime indie, Steam Audio and a bevy of marketplace assets are intended for PC/Windows only.

Microsoft updated Xbox to Windows 10 a few years ago, UWP games now run on Xbox (xbox play anywhere) (Unreal works fantastically with UWP, GoW4 is the only UWP game that works properly on Windows 10), and the upcoming Scorpio which can pretty much run any game at max settings. What is stopping a developer from using the assets listed in the second sentence? Why wouldn’t they work with Xbox, if Xbox is Windows 10 and if I just package my game in UWP?

I would like to release a game on Steam in Win32 and the Windows Store in UWP for the Xbox Play Anywhere program with cross play between both services.

Note: I am not looking for a debate about UWP and Tim Sweeney.

UWP would require specific support, those are two different platforms. Alternately, even though Xbox runs a version of Windows 10 it’s still essentially its own platform which is why there’s a version of UE4 that’s specifically for Xbox.
Just so you know, the Play Anywhere thing is just a promotional thing–basically giving you both the Windows and Xbox versions along with having cloud save file support. You would have to work with Microsoft for them to be interested in making your game a part of that. And as for cross platform play–that’s a different matter where you’d have to work with Microsoft to help get that system together, which I would think that Microsoft is would be only really interested in doing with a game that they’re publishing.

With a UWP game you could release on both Windows and Xbox One with minimal changes. But you have to use Microsofts custom UE branch for it. Most assets marked Windows will work on OS X, Xbox One and PS4 as well. In most cases the platforms only tells you on which platforms it has been tested.

Afaik you can already have your UWP game be buy once on PC and Xbox, as well as have shared cloud saves. That do not require any special deal with MS.

Play Anywhere is targeted at native Xbox One and Win32 games. And MS definitely wants to have other publishers using it.

They don’t work because they are Windows platform, not UWP. They’re Win32 / Win64.

I’m talking about cross-platform play, since it would have to connect to Microsoft’s online system being able to have people on PC play with people on console would require working with them to get that going, and I imagine they’re more inclined to do that for their own games.

Cross platform between Xbox and PC has been possible for over a decade through Live, or by having your own services infrastructure (e.g. Rocket League) - people don’t do it for a number of reasons though.