Why would Vulkan, as opposed to a custom solution designed to target that hardware and games specifically, be a better solution?

Vulkan came to be as a low-overhead rendering API targeted at 3D video games made originally, as Mantle, by both AMD and DICE.

If anything, I'd see any console or game people involved with this as a bad signal, considering what a travesty Vulkan came to be and that one originated from such a group.