I don't own this game, but twice I have switched positive reviews to negative for doing this.

On the one hand, it's a shame in general, as Proton has truly been a pesky thorn on the foot for Linux gaming. There's a world of difference between having native, first-class support, and basically running every game on an emulator that is on a lease.

"Drops the Linux build to focus supporting proton" makes as much sense as "drops the windows build to focus supporting direct x in wine"