What you say here could be very interesting.
Is that page on the broad subject that it is appearing at #1 for?
Staying with the assumption that CIRCA is the silver bullet. Pure speculation but, perhaps an element of what CIRCA does to pigeon hole a page is to look at inbound link anchor text. If that text uses the exact term and the page pointed to is about the broad context then perhaps it is seeing that page as a good match for the broad context of what is being searched for.
If you want to stikie me details I would be pleased to take a look.