So we here a lot of things from different people in Aikido about why this and O'Sensei did that, a lot of it contradictory. From one sensei, who trained with one of O'Senseis students, I've often heard that Jo came from O'Senseis training in yari, and naginata etc. And O'Sensei did this because the sword is predominantly used in a right foot forward kamae and so as to balance this the jo, as OSensei taught, is used from a left kamae. And hence the reason for O'Sensei developing jo movements and using both weapons.
Now this makes some sense to me, as a lot of Saito's kumijo are from the left foot forward. Has anyone else heard this theory? Or maybe this an interpretation of O'Senseis intentions after the event thing?
Ellis's account in Hidden in Plain Sight,
filtered through me, is that Osensei's training in bayonet was probably the most important influence in the developlment of the paired jo kata. The Yagyu Shingan ryu that he practiced a bit was the Goto-ha line. Ellis asked the headmaster of that line what he thought about Aikijo and the Soke definitively stated that there was no way that Aikijo was Yagyu Shingan ryu.
(Note: don't assume I am giving you an authoritative gloss of this section just because of my first name - you should read the book yourself.)
I haven't had the time to verify what line that youtube clip I posted is from, but the bojutsu certainly looks MORE like aikijo than, say, Shindo Muso ryu, which is what an actual combative jojutsu looks like IMO. I am given to wonder if there are any imaginable circumstances in which the headmaster of a highly esteemed koryu would ever watch a demo of some gendai budo weapons and say "Oh yes, clearly they are practicing our system."
As far as "the sword is predominantly used in right foot forward kamae" ... if you are talking about back in the day
, then this is certainly a mistake. If you are talking about in AIKIKEN, then....why create a whole other weapons system to emphasize left foot forward? Why not just practice the sword with left foot forward sometimes?