All I know is that I can apparently play and install Xbox games on SteamOS now using a vibe coded app.
This is a different issue and has nothing to do with Play Anywhere. They reverse engineered the XBOX libraries to be able to login into XBOX and use the API to connect and play the games native on Linux (including SteamOS).
Play Anywhere exist about 11 years now, but it was named Live Games before. They changed the branding to Play Anywhere later, but its the same since launch. https://en.wikipedia.org/wiki/List_of_Xbox_Live_games_on_Windows_10
This is a different issue and has nothing to do with Play Anywhere. They reverse engineered the XBOX libraries to be able to login into XBOX and use the API to connect and play the games native on Linux (including SteamOS).