Why can't i just shake the feeling that Steam Machines will Valve's gateway to release Half-Life 3 as a Steam Machine title exclusive? Furthermore, HL will only be Linux exclusive, at least for the first few months to put pressure on Sony, MS and Nintendo and the GTA6 launch.
Why it feels like "this year will be the year of Linux desktop" didn't sound absurd enough for you so you went and upgraded the idea to "HL3 will be a Linux exclusive."
I just don't see that happening, aren't linux users only like 5% of the user base? Releasing their most anticipated title only for the minority would make them lose out on a hefty amount of money. The more realistic option I see is that they offer some exclusive content (add-on or cosmetics) for SteamOS users.