treeline - 8:08 pm on Jun 14, 2013 (gmt 0)
The results (for my site / forum) show that the public SERPS appear to use a setting of 'basic + a fraction'
Well....that's roughly what is at the top for many terms, for others it's the intermediates, but the advanced are on the first page for many terms.
What I think is happening is this filter isn't used at all on normal search results pages and that these happen to be the pages that are "most useful" according to Google's normal thinking.
Sort of like on advanced image search you can ask just to have small, medium, or big pictures.