This is an interesting take, especially coming from a non-gaming focused tech website like Ars Technica. I feel like it’s been too long since people were truly hyped about half life 3 though, and this wouldn’t be enough, even if Valve did go through with it.
People are increasingly unhappy with windows though, and the EoL of windows 10 may push people to Linux anyways.
Making HL3 only GNU/Linux exclusive would be the gigachadest thing ever done. Well even better than exclusivity. Make the game playable on windows but only with a downgrade in performance or need of emulation, like the whole industry has made with GNU/Linux.