Also, I never argued against Proton having been a boon for Linux gamers, but I tried to present an opposing point of view that usually does not get taken into account.
Like I mentioned in the other comment my impression over the past 3-4 years is that the number of native linux ports has dwindled to nothing and that is most likely due to Proton making them unnecessary.
Without Proton the steam deck would not be popular enough to warrant any Linux ports either way. So Linux ports would be doomed regardless.
The real travesty is steam, with the recent introduction of WoW64 in Wine, is now the only software that requires me to run 32bit binaries on my desktop. Real annoying.
Is your argument specifically about the game developer's mental model for Linux's priority, or something core about the Proton abstraction layer?
All software runs on some abstraction. So specifically, if the game developer prioritized a Linux port by explicitly testing Proton, would that be enough for you to consider the game "developed for Linux"?
Regarding games, that is a binary that targets the ubuntu based Steam Linux Runtime. That's what I meant when I said that devs should be able to target it as a regular console SDK.