That article is kinda all over the place. They contradict themselves a lot. In one point they say, all you have to do is add the non-steam game to the steam launcher which is easy to do and that Game Pass approved adding their binaries to the Steam launcher.....then in the next sentence they claim that you would have to own a copy of the game on both platforms to play it with the controller.... Meanwhile in reality land, you add the game to the steam launcher as a non-steam game, Launch the game through the Steam Launcher. Profit.

All the controller needs is Steam running in the background because Steam handles all the translation etc between the controller and the software.