I'm a bit puzzled by what's the news here. You're basically proven an axiom : in any CPU were you have resource sharing among 2 threads, running only one ( thus giving it the whole resources ) it will run better.
If you take a Core 2 and disable 1 core, rest assured, the performance of that one thread will be better than running the same thread with both cores active.

The whole point of AMD's aproach is to avoid exactly that : don't make a fat core ( what you're suggesting ), but skinny ones and lots of them. On desktop, as BD has proven, this is a failure.

AMD could have created BD as a 4 core with each module being transformed in a fat core, but that's SB reloaded.