Speculation.
Again, can we please look at what happened or some of the claims that were being made prior to Bulldozer?
Dresdenboy has amazing technical competency and understanding of CPU microarchitectures, but like everyone else NOT part of the actual AMD Zen microarchitecture design team, he can only speculate on Zen's per core, per clock performance.
My concern with Zen's performance is that AMD has been extremely tight lipped. This is unusual if or when a company has an upcoming product that seems successful. For example, Intel previewed Conroe's performance at IDF 2006 (7 March 2006):
http://www.anandtech.com/show/1963
http://www.anandtech.com/show/1966
Conroe was then launched sometime in July:
http://www.anandtech.com/show/2045
Then again, Zen may end up being an RV770. But that kind of secrecy preceding a successful product launch is more of an exception than a rule...