I drive my mom's NAH every few weeks but am unsure if I feel what you're describing. I will say the NAH's power transitions are more abrupt than on my Prius and it feels like it cuts the gas engine more agressively/the cut itself is more aggressive.
Perhaps you can borrow someone's ScanGauge
to watch the engine RPMs since the NAH has no tach and also look at ignition timing?
To be slightly OT, people believe the Prius has 5 stages of operation (see PDF attached to http://priuschat.com/forums/knowledg...rence-aid.html
). I can confirm some of this on my Prius since I recently got a ScanGuage, esp. the change of IGN going from -10 to something >0. I wouldn't be surprised of the NAH similar stages (it definitely has stage 0).