You're performing advanced searches though, correct? Google seems to know about a lot of things but, it is only going to display those things that are most relevant to the query. In advanced search queries, that is a completely different ballgame as you are seeing things that the typical searcher does not.
So, in the scenario you describe above, is it possible that Google has determined which of those 200,000 variations is the authority and will show that a majority of the time for who knows what type of searches. And then, for more long tail queries, one of those 450 results now come into play?
Sitemaps are another tool for Webmaster to utilize and control the flow of what is and isn't getting indexed. They are a great addition to the "funneling" and/or "sculpting" process. Take a site now that is having a tough time from an indexing standpoint. Build sitemaps for the pages that "should" be indexed. Drop a robots metadata element on those pages that shouldn't be indexed. Get the bot to "go with your flow". Multiple sitemaps are an integral part of any large scale website.