Hm, I thought that was pretty clear. Maybe this helps? http://c2.com/cgi/wiki?WhatIsRefactoring in particular the section on the differences between refactoring and rewriting. I don't think you'll find anyone claiming Plan9 is a refactored Unix. It's always been a proud start-from-scratch effort.
My lament is that, at this point, Plan9 is dead in the water and its team members are using Unix in their day jobs again. If it had followed a longer, more conservative schedule, maybe starting from a working Unix base, it might have seen more success. Ah well. Now it's competing with Haiku and the Hurd for the cleanest software that nobody uses. :)