Well Stadia themselves have barely started making first party games, whereas Valve not only makes games, but also makes their own game engine, and have for deca

Well Stadia themselves have barely started making first party games, whereas Valve not only makes games, but also makes their own game engine, and have for decades. These improvements you see on Linux have been over 8 years in the works, Stadia has only been around for a year. I would also assume that by getting devs to port their games to Linux to run on Stadia, the contribution may be more indirect. You'll get more game studios contributing to the stack, even if Stadia themselves aren't yet.