Earlier quoted context omitted.
Valve is an oversight, yeah -- I did mention them in another comment here. I don't really think of them as a game developer anymore, but I'm probably being unfair. If Apple supports Vulkan but with worse drivers than Metal, I'm not sure that's any better. OSX has roughly four times the penetration of Linux in the latest Steam hardware and software survey. I'm not sure it's worth it for most developers to deliberately…
I was talking more about Vulkan's second-place position on Windows than about Linux (Vulkan is likely to have some advantages on Windows, like being less tied to the Windows roadmap than DirectX, or indeed OpenGL), and if Apple provided bad Vulkan support I think they'd just be letting themselves in for bad Vulkan-based ports. But overall I don't think we're really disagreeing very much here. (EDIT: see below.)
[1] http://store.steampowered.com/hwsurvey [2] https://community.amd.com/community/gaming/blog/2015/05/12/o...