The HL3 memes don't even seem fair to use anymore. I don't even want to un-seriously make joke fun of them at this point. They are just genuinely doing so much for the community.
Some of it is counter-productive though. Proton made WINE commercially viable, and in doing so, disincentivized native Linux builds of games to the point that some studios that had been releasing games natively for Linux have stopped doing so, since the Windows version now plays well enough under Linux.
No, not really. Many of the common game engines already support Linux out of the box. Unity, for example, already makes building for Linux basically equivalent to building for Windows or Mac. Proton has disincentivized building for Linux even in cases where doing so is already as straightforward and low-effort as could be.
> Or, is the gripe about distinction of released for vs playable on?
Yes. Most of these games were already playable on Linux under Wine, even if it took a bit more effort on the part of the user to get things up and running. The rise in Linux usage started motivating native Linux ports for a few years, and there's a large library of native Linux games out there. But Proton has been removing the incentives to build native Linux ports by making that Windows compatibility "just work".
The result is now that there are more games where Linux compatibility still running on top of an emulation layer -- but one that's a bit less straightforward for users to configure directly as they would with Wine -- and a bit less performant than they might otherwise be.
It also means that Linux compatibility for these games is more closely coupled to the Steam ecosystem. Whereas a game with a native Linux build might distribute that build through Steam, GOG, Humble, itch.io, etc., now the non-Steam platforms have only Windows builds. Sure, these can usually still be played under Wine in the traditional fashion, but that represents a regression away from native Linux support.
Realistically a lot of devs aren't going to make Linux versions at all (or be able to spend time actually fixing issues with them) unless Linux users make up a bigger market share. Valve's efforts are helping to grow Linux market share, which is a necessary step before we can ever hope for most devs to focus on Linux compatibility.