Indeed, this gives a little credence to Honda's 3 year old statements that HEV technology offers significantly diminishing returns in fuel economy for larger platforms - which soon begin to erode the benefits of the technology.
Until now, this corollary has not been proven wrong even with the latest HEV and the soon to be released models (2-mode included) from the GM consortium.

If this remains true, then the question then becomes what is the "sweet spot" in terms optimal FE and size that a platform must have in order to maximize the benefits of the HEV tech?
At the moment, I believe the Prius II is closest to offering the perfect balance of size and FE.

Cheers;

MSantos