[21]

NVIDIA/AMD drivers with Vulkan support pass through WHQL, which is as official as a 3rd party driver can get.

So calling them unsupported/unofficial is quite a stretch.

[MBCook]

Does WHQL actually include any Vulcan tests? The driver may be officially certified but is the featur in question?

[ioquatix]

What's probably more relevant is that those drivers pass the Vulkan conformance tests.