Re: Hombu Culture
No, the 31 jo kata and all the other ones you mention came from Saito, authorized by Kissomaru Ueshiba, of course. Saito took years trying to get all the jo basic moves into one kata. and he finally came up with the one you see.
My school was in Asuma Air Basse, under Isoyama, uchideski at Iwama since he was 12, the youngest 6th dan aikika ever (25) So, we were learning Iwama style as early as 1963.
.We were technically under Saito, because o'sensei wanted Saito to teach Isoyama, but we never saw Saito, unless we went to Hombu, Saito couldn't come to Asuma, he didn't have a military pass.
We did a lot of techniques different than Saito. Techniques that Isoyama thought were more like the way o'sensei wanted them.done.
Nishio was older, eleven years older than Saito, and his techniques are great. Very powerful. He learned them all from o'sensei, of course.
Where and when and how Nishio spread his techniques to the west, I don't know, but I think they were mostly from seminars..