I have followed this thread for a while now, and the more I read I think it is a purposed design. I think that maybe in the same vein that Nissan wanted better MPG and henceforth did not include front brake ducts that would have decreased mileage due to drag, perhaps Nissan mapped the throttle in such a manner that if not fully depressed at launched at a high RPM, the car sips fuel below 3000 RPM. Further that with the torque curves seen in just about every dyno map done on a stock 370z, with a huge dip between 2500 and 3000 RPM, and the hesitation makes perfect sense - not that it does not suck.
It is ironic that a simple fix such as the gadget that increases voltage to the gas peddle is all that is needed to overcome some of the hesitation, but the inherent design of the engine and mappings make it fairly difficult (or at least some serious investments) to overcome.
Car and Driver Investigates Brake issue
Z Meets Wall: We Investigate Why the NISMO Z's Brakes Failed at Lightning Lap - Feature - Auto Reviews - Car and Driver