Releasing an actual Linux binary doesn't really matter that much. Proton is just a better experience. Even when games did include a linux build you were usually better off telling Steam to run the Windows one in Proton because it just ran faster with less bugs. A Windows binary is just more portable, more stable long term, and a better experience.

What we actually need is developers testing their games on Proton to make sure they run well day, releasing graphics presets that run well on the hardware, and simply not blocking Linux through anti cheat.