Re: origins of the kumi-jo (again)
Saito himself goes into some detail on the evolution of the forms in the "Aiki Jo" DVD (Aikijournal), including when and why he added some of them. I believe he also states that the 13 jo kata was the first one that Ueshiba showed him, but that he never showed him a kumi jo for that kata (unlike the 31). But, as implied above, Saito rigorously — almost obsessively — sought to preserve and present Aikido exactly as he learned it from O Sensei. In the absence of specific technique, this would leave the Really Important Stuff: principles; internal consistency; spirit.