Well, that doesn't matter in the end. Part of extend is to take whatever you embraced, and add things you cannot do. So it's a success in that sense. Seems you're trying to put it as "What can Microsoft do if Linux doesn't support it?" when they can, if they want to, do plenty about it.
> bringing dxgkrnl to Linux would have been a much more involved process instead of just providing a redirect
Of course, that's how collaboration works. Instead of going the harder but "improving the entire ecosystem" way, Microsoft chose the easiest + the one where they can extend stuff in a non-compatible way.