If you draw a 2-dimensional chart of low-levelness vs performance, Vulkan, DirectX12 and Metal are all higher performance and lower-level than OpenGL. Metal is a bit higher level than the others and Vulkan is probably the lowest level, but they are about the same performance. WebGPU is a bit closer to the Metal level than the Vulkan level, but it's still lower-level and higher-performance.
Why not write a blog post, comparing a hypothetical: WebMetal vs WebVulkan?
Clearly there is a lot of misunderstanding, or at the least passion in regards to Vulkan and Metal. Rather than disregard it as "yeah, we thought about it.. but no". Why not actually help educate us?
> "Metal is a bit higher level than the others and Vulkan is probably the lowest level, but they are about the same performance"
The above is what you claim, but why not actually put it to the test? Compare the two in an open forum, have a fact based discussion, hopefully including benchmarks and code examples, and come up with conclusions. Allow people to correct you (where appropriate), and write a follow up blog post with conclusions.
You seem to also have another point, "Even if Apple supported it, Microsoft doesn't, and therefore WebKit couldn't implement a hypothetical WebVulkan". That's a fair conclusion, and would push the pressure from Apple over to Microsoft, and at that point no one could fault Apple/WebKit from proposing a different design. However, as it stands (i.e. without an open conversation/comparison), you while clearly educated on the matter, come across disingenuous (I'm sorry to be pointing out the truth).
