Microsoft has made such a mess of controller I/O that they were kind of forced to go with their jank translation layer made from scratch and running with their main product - it makes sense, especially built up piece by piece

Of course now that they've made controllers work properly, they'll use that work to support their own controller, and in particular enable features like analog triggers + gyro aiming + rumble (xinput can't do these simultaneously), extra buttons (xinput can't do this), and the trackpads (you guessed it).

And it is Windows, because on Linux the controller does work without Steam if you get the right drivers. It doesn't get the full features but it's functional as a gamepad, at least.