As you pointed out, the National event is run on a concrete surface, most Regional events are not. Yes, the Index is used for some things at the Nationals, but it is more often used by Regions on an asphalt surface (hundreds of events). Also, as Jeff pointed out, percipitation played a big part in several of the Street classes. The National Championship event is a very worthy data point, but it is just one (or maybe two) events.
As you may know, I had recommended a factor of .975 be applied to the Street classes (including Street Touring) for concrete surfaces. I may post a different set of results that incorporate that factor. We'll see if I get time for that. I'm currently very busy working out the factors for next year. There may be some major shifts, but not necessarily in the way you hope.
Thanks for the thanks, with Numerous H's & K's,