We improved the crawl frequency and decoupled it from which index a document was stored in, and once these "supplementalization effects" were gone, the "supplemental result" tag itself—which only served to suggest that otherwise good documents were somehow suspect—was eliminated a few months ago. Now we're coming to the next major milestone in the elimination of the artificial difference between indices: rather than searching some part of our index in more depth for obscure queries, we're now searching the whole index for every query.

http://googlewebmastercentral.blogspot.com/2007/12/ultimate-fate-of-supplemental-results.html

I'd reformulate your headline: Google now fully integrated those more obscure documents which were formerly shown less or shown differently.

Anyway, very interesting pointer!