Yup, nothing to magic, just the usual symptoms of Windows and Linux have always had different ideas of how files are supposed to work, so give Linux its own (virtual) hard drive instead.
I don't know anything directly about Microsoft's 9p plans, but the blogs give an impression they are considerably pleased at the 9p file server for what they've been using it for (especially these cross-platform communications) and they might use it for other things.
I really "like" or at best have mixed feeling of Linux/POSIX way of handling file in use, can be deleted/moved/edited, like EXCLUSIVE LOCK means nothing to the system.
Windows took a very different path from POSIX for a lot of reasons. It frustrates me sometimes when some Linux fans insist that POSIX file system semantics are "the best" and "the only right option" simply because they've been ingrained in more than a half-century of Unix development practices. The NT Kernel team was certainly aware of POSIX file systems and their trade-offs when they built the Windows file IO libraries and made different choices for good reasons. POSIX isn't the last word on how file systems should work, some open source developers should learn that, I think.
You think there's any chance Microsoft ever expands their 9p support to allow users to mount arbitrary 9p filesystems?