I quite agree with you. I have always understood 'grounded conductor' to mean a conductor that is _intended_ to carry current, as opposed to the 'grounding conductors' which should _not_ carry current in a properly functioning system. The above interpretation is what I get when I read the literal wording in the code.
This does lead to a logical conflict, since an equipment grounding conductor is also a 'grounded conductor', and therefore required to be white and green at the same time.
How about another funny: if you don't buy that the GEC is a grounded conductor, and by definition the GEC is also not an EGC, then you get to 'the GEC may be any color'. However, based upon 310.12(C) if you use a particular color for the GEC, then you can't use that color for an ungrounded conductor. So your use of the black covering for a GEC means you can't use it as a phase conductor