It is the same stance as calling Windows games, developed for Windows, using DirectX, without any consideration of the studios to ever target GNU/Linux, even though they might actually target Android/Linux with other titles, Linux games.

Because somehow Proton is better than standing for actual GNU/Linux games.

So like IBM with OS/2 and Windows, studios keep ignoring Linux, and let Valve do whatever is needed, it is Valve's problem to sort out.