October 26th of this year, I wrote an entry named Supplemental Result Are Keyword Based based on a WMW world post. It seems as if, a point made in the thread and in my entry is not 100% accurate. Danny Sullivan sent me an email stating "Supplemental results should indeed be pages that are actually live on the web."
Danny goes on to say
Yes, heard from Google, the pages are definitely reflecting what's live on the web. If the terms aren't present, it's just that they haven't been revisited, not that Google is trying to use the SR as some type of archive.
For more information on some of the mysterious qualities of the Google supplemental results, visit http://searchenginewatch.com/searchday/article.php/3071371.
Sorry for any confusion and thank you Danny.