Official Proton support is an excellent, functional compromise.

Except it's not a compromise. 99% of games on Steam work on Proton without input from the devs. All they have to do to make it work on Proton is to not go out of their way to break it. At most, they probably have a single Linux system in the studio to run builds on just to make sure it works.

They're doing nothing in this regard and pretending they're doing something for brownie points. If you don't want to put in effort to make a separate Linux native version that's fine, but don't then turn around and claim that you're focussed on Linux support.