longer poles are supposed to make the BL more symmetrical. SO when the sub moves out it maintains more bl then if the pole was shorter. Using a longer pole also reduces the overall bl as a compromise but i'm not sure how much....not a whole lot.
As to which is the latest motor....based off intuition, i'd say that it could go either way:
They could have first started with the shorter pole and figured it would sound better distortion wise with a longer pole....Or, they could have started with more linearity in mind with the taller pole....but figured damn, the bl is too little with this long of a pole.
Even the shorter pole is a decent height..