steveb - 8:34 am on Nov 12, 2006 (gmt 0)

"Simple as that."

Hardly. And "unique content" is not necessarily what makes supplementals. Any page that has no www 301 redirect can end up ignored and the wrong URL, the supplemental one, the one that is dominant.

However, unless something has changed in the past few hours, it still remains impossible for a page to get a fresh tag and be supplemental. If you have a URL that gets crawled and doesn't get indexed, you have a problem. The supplemental index is separate from the main index. Pages that get crawled get put in the main index, unless Google has a reason to discard them.

Every supplemental page I see gets a normally indexed page two days later if you point a decent link at it and get it crawled.

This says nothing:
"I have and have seen several sites with extensive and accurate internal linking structures, and usually Google sitemaps, so all of the pages do in fact get crawled."

When in fact was the page crawled? If it was more than two weeks, the regular page may be dropped and a supplemental the only thing shown.

Test it out. Put up new pages at the same linking level as a supplemental page. Make sure it has a 301 on it, a unique title and description, content on no other URL, and enough of the "content" part of the page to be dominant over the navigation/template part... and then see if when it is first crawled it appears as supplemental result. No way, not ever.

On the other hand, if the page is something like the millionth copy of an Amazon feed page, with www and non-www versions, with no unique description, well then it might go straight into the supplemental bin and stay there.