They’re probably building off Windows RT (the locked down variant designed for ARM tablets).

If they were smart they’d imitate some of how SteamOS runs games in a modified WinRT environment - TLDR do NOT start up the entire Win32 runtime and desktop environment by default, don’t run stuff like printer services and whatnot, just run a simplified sandbox and window manager with just the APIs needed to run the games similar to Proton. Then let the user switch to desktop mode as needed, but don’t run it when gaming.