Earlier quoted context omitted.
That only works if studios ever bother to write native Linux games, otherwise is like being happy MAME supports Linux.
Proton is a platform. If Valve gets gaming studios to target proton and guarantee compatibility, is a win. If that's equivalent to gaming studios explicitly targeting MAME and QAing it, I'll take it.
Anyway it hardly matches Switch sales, for which studios do actually bother to actively support.