My 12V battery was the original Japanese item fitted back in 2013, the voltage was fine and the indicator shows as healthy but I bet it wouldn't perform well if load tested, have seen it a lot on ICE vehicles except it's more noticeable as the vehicle won't start
I see there is a servo that controls the hydraulic pressure according to an algorithm and acts as a booster (instead of engine vacuum), it's as though this pressure suddenly spikes causing the grabby feeling.
I still get a little bit of the grabby feeling occasionally but it's no longer at the crawling speed which would cause the vehicle to jerk to a halt which was very annoying for me and any passengers.