> Vulkan is an open _standard_

That too kinda depends on where you draw the line, the spec text is freely available but all development happens behind closed doors under strict NDA. From an outsiders perspective it doesn't feel very open to get completely stonewalled by Khronos on the status of a feature that debuted in DirectX or CUDA well over a year ago, they won't even confirm whether it's on their roadmap.

Sure, that's true and a pretty valid criticism of the system.

My definition of open is that Khronos doesn't restrict (as far as I know) what platforms Vulkan can be implemented on. The same cannot be said for DX12 or Metal.