It's only been 4 months... but this is a basic issue and the thread was left unanswered, so I believe it's worth updating.
Basically the Source Settings / Debayer Detail control has little (nothing) to do with debayer resolution as we know it from RedCine-X and elsewhere. It's just a rather subtle sharpening control. Actual debayer resolution is automatically controlled, at least in CS5.5.
This didn't seem to be documented anywhere that I could find, the most official answer came from Steve Hoeg at Adobe's forums.
Andrae Palmer did a lot of digging to find that out and deserves the credit.