To be honest - I have no idea
- but then historically, even Dx9 never went the .1 route - using instead the a/b/c route (if memory serves?).

I don't think that DirectX is viewed in the same way now as it used to be (notice the lack of any file-version data in the dxdiag report nowadays?), and that it's considered a minor part of the OS, and updated as such. I can't remember seeing any directx-specific updates in the listing since Vista was released.