It's still cross platform, just across Linux and Windows, doesn't look dishonest. It's similar to other "linux/macos"-only tools that also call themselves cross platform.
The baffling part though is recommending using homebrew to install it on linux.
Nah, I know about Racket's DSL support and touting itself as friengly to language writing, but it's still not the same as a dedicated parsing toolkit, the same way I wouldn't consider a Lisp with reader macros equivalent either...
... but racket basically exists to create parsers and languages. It happens to also be a general programming language. But so is JS nowadays with Node.
How is Proton a technology/library/sorftware? I got the impression it's just a preconfigured Wine, but not an actual implementation. Sorry if I'm misinformed.
And _if_ that's true, I'm sad about the credits not going to the Wine team.
The 'secret sauce' is actually 'Steam Play' which is the automated wrapping, configuration and execution of Proton wrapped games without the user having to do anything (other than a confirmation box to confirm that a compatibility layer is being used).
The Steam Play component turns it from a 'nice meta-distribution for wine' into 'killer quality of life improvement'.
I guess it somehow makes sense for Valve to keep the per-game tweaks private. With all of that money they're printing though, I sure wish they could feel that they could afford to be less defensive.
None of it is private. The per-game settings are all listed here, the options are all implemented in Proton, which is completely open source: https://steamdb.info/app/891390/info/