I don't think the best way to develop for Linux is by making a windows binary, I think the best way for game developers to make a Linux version of a game they otherwise wouldn't is by making a windows binary compatible with proton

Problem is very few developers actively choose to make a Linux game and windows games if done right run at native speeds on Linux anyway.

I'm gonna be unpopular for saying this but it's the same thing as using HTML for desktop/mobile apps, sure it's not optimal performance wise but it's a hell of a lot better than often nothing at all because companies can't or won't justify development time to support smaller groups of people on smaller platforms

If such a time comes that desktop Linux has a large enough market share for large companies to take seriously then I'm sure they'll start developing native versions of maybe even make Linux-first games but sadly we're nowhere near that point yet so best we can hope for is good cross compatibility tools