There is "official text" and "clarification of official text outside of the official text". The 2nd is almost never done ... and clarification is only obtained by changing the official text. It is possible that Red Hat was simply more specific/clear when they created their original text. However, if I recall correctly, RH actually rewrote their official text when CentOS (and its predecessors) began. Believe me, Red Hat was vilified at the time and their behavior, IMO, was worse than Canonical's today. [e.g. The last RH iso I used was Red Hat 5.2 (this was in 1999 and before RHEL and Fedora existed). I paid $50 in 1999. At that time their installer was proprietary ... so you couldn't redistribute the ISO! Think of that in today's context.]
If someone actually went to the effort to create an Ubuntu clone via recompiled binaries (and also removed infringing use of trademarks ... and affirmatively asserting that this is "not Ubuntu"), just as when CentOS was created, the text would be clarified. And, frankly, contrary to what Matthew asserts, this would not be terribly difficult (not "easy" but easier than CentOS").
Re: Comparing to Fedora / Comparing to Red Hat
If someone actually went to the effort to create an Ubuntu clone via recompiled binaries (and also removed infringing use of trademarks ... and affirmatively asserting that this is "not Ubuntu"), just as when CentOS was created, the text would be clarified. And, frankly, contrary to what Matthew asserts, this would not be terribly difficult (not "easy" but
easier than CentOS").