Never seen a page with TBPR that's also in supplemental. My assumption would be that the realtime
PR is zero and this will be reflected in the next
PR update. Thanks for posting as it's an interesting phenomena!
With regard to the supplemental index as a topic, I have this very problem. Over 95% of the pages of the site I work on are in there and traffic from Google is relatively non-existant. Close inspection shows that Google is now imposing strict duplicate content filters. If you think about it, this isn't really all that surprising but the implications for e-commerce sites who use data feeds (cNet for example) for product data are in a spot of bother. I'm now working on a totally new site, and have bitten the bullet so to speak. If I want my pages in the main Google index, they have to have LOTS of unique content and no duplicate. Google is telling us the days of automated stuff are over - create something original, or don't get listed.