Don, could the front end be longer in order to move the front seats further forward? In the current Volt it seems like the firewall is further back from the front bumper due to the fact, probably, that there was simply so much to fit into the engine compartment that they had to move the firewall back 3-4" and then the drivers seat got moved back 3" and the rear seat lost a great deal of its legroom.
So in the Gen II Volt they may have decided from the git-go to shift the engine compartment further forward, thereby allowing for the firewall to move forward as well and in turn, allowing for the front seats to move up thereby freeing up some backseat space.
Obviously, that is just conjecture, but it sure does seem that the front end has gone through a Pinocchio like growth...