They appear to be in genre priority, from least to most specific (generally). garyan2 linked me to and old TMS document (also found at another site), the previous top level category element was pretty much and exact match to those old genres from 2006.
I'm good with the order and the data, it's like the channel display-name elements, as long as the order is predictable it works as-is. No need to change anything that was just a general annoyance about the loose schema .
The TMS document did reference they used a priority flag for their genres, if an attribute was present to indicate that I could also just find the second highest. But again, no need to change anything!!