But games that run on linux via proton have not been compiled for linux, so mentioning them as a counter-argument to games not being compiled for linux makes no sense.
The broader context here is TFA rejecting the "steam runtime" idea, and for proton-based games proton is that runtime! They don't need anything from the system because proton/wine provides it.
linux native + proton means "some compiles for Linux[1], the rest either tests on proton (steamdeck should increase that segment at least) or does not care"
The games that run on proton have not been compiled for linux.