Why is vkd3d an extra projekt?

[Fabian Maurer]

Hello,

For a while now I'm curious, so I have to ask: Why is vkd3d an extra project?
Is that because it is reusable as standalone library? Just curious, because
it's the only library in Wine that is a separate project.
Wouldn't it have made sense to develop it as part of Wine to reuse the wine
infrastructure and always have the most recent code for dx12/shaders?

Regards,
Fabian Maurer