No, you are the one still not getting how the game industry works.

Those game engines support the graphics APIs from, PS3, PS4, PSP, PSP Vita, Wii, 3DS, OpenGL, DX9, DX10, DX11, DX12, WebGL, Metal, Vulkan.

Adding support for Vulkan is just yet another bullet point on that list, just like they are busy adding Metal support, as it was discussed at Unite LA.

The people that actually use those engines to make games, don't care what APIs are abstracted by those engines, as long as, their game is fast, takes full advantage of the GPU and targets the game system they want to sell to.

No, you don't get it, since adding anything to the list increases costs and slows down development. But I guess since you aren't working on those engines, you just assume magically adding a bullet point is all it takes.