I don't know if Chris is ever getting around to posting a reply in this thread, but I happened to be looking back through the original discussion and found this quote which seems relevant to my points:
Chris expresses the opinion that Jethro Tull's genre was wrongly categorized by the Grammy's. Here's the thing though - musical "genres" are primarily marketing categories, not inherent, invariant attributes of the music. This is why the same song might end up classified as "rock" when performed by a white artist or "blues" when performed by a black artist. (Or as "country" if performed by a singer with a twang and a pedal steel in the background.)
In the specific example he gives, the best classification for Jethro Tull is, well, just Jethro Tull. They combine elements of folk, blues, jazz, classical, rock, proto-grunge, proto-metal, and really just anything that strikes Ian Anderson's fancy. You could call that synthesis "prog-rock" if you want, but that's really just a marketing category. You wouldn't confuse a song by Jethro Tull with one by ELP or Genesis any more than you would confuse it with one by Metallica.
Labelling music by genre can be useful either for marketing or as a shorthand for making broad generalizations about aspects of music that you like or dislike, but that's about it. Genres have boundaries just as fuzzy and imprecise as any other label. That fuzziness isn't just a feature of artists who blend multiple stylistic elements. Quick quiz - what genre does Johnny Cash's cover of "Hurt" fall into? It's a cover of a rock song written by a rock artist, but it doesn't contain any of the elements you would normally list as typically characteristic of rock. It's sung by a singer who is normally lumped into the "country" genre, but it doesn't contain the typical signifiers of country either. If you came to the song knowing nothing of the singer or the original composer, probably the best descriptor for the song you could find would be "heartbreak." It's just music, expressing pure emotion, not bound to any particular pigeonhole.
As might be gathered from my previous comments, this is how I think about martial arts as well. "Styles" can be useful tools for organizing a training curriculum or examining the historical evolution of martial practices, but I don't think that it's helpful to view them as rigid boxes that confine the practitioner.