It seems you haven't read my post history here. But yeah, AMD has been been inside the Linux community for quite a while. Things work different in Linux compared to Windows, if you want future proof hardware support you have to get your drivers into the official Linux since there is no stable ABI.
And Valve has invested a lot in the "Linux" eco-system from gamescope to proton to drivers.
Also, there is still independent people implementing HW support for Linux, look at the Asahi project for ARM macs and novoeu for nVidia.