That wasn't a starting battery... that was a lead-acid 12V accessory battery. Just a buffer for the DC/DC converter. If the final version of the car ships with one, I'd replace it with
one of these little guys:
Also, while the EV1 was a new car from the ground up, the Leaf rides on a modified Versa platform. There's nothing wrong with platform sharing, just things wrong with Llewellyn's facts, as usual.