That is one of the things that puzzle me. Didn't all koryu arts also deal with weapons? Be it defense against weapons or having a weapon curriculum?.
By this link http://www.koryu.com/guide/takenouchi.html
, Takenouchi ryu also had various weapons curricula. The only koryu that i can think of that didn't have techniques with weapons was Kito ryu and even those throws were officially presumed to be done in full armor.
By the standards presented also by you in your book Dueling with O'Sensei AikiBudo was definitely not a koryu. I don't know what was Hirai doing at the time but if it was similar to what we know today as Korindo Aikido it was also most definitely not a koryu. Did they basically just try to take out all of the taijutsu techniques from various arts and group them under one singular term? Also would that mean that many arts of the time actually had some mentioning of a term similar to "Aiki" in them?
This would seem to be the only logical explanation.
1. Kito-ryu used to have a variety of weaponry in its curriculum
2. The term 'koryu' was a fluid term. And a focus on when ryu were developed and defining some as koryu and some not is a modern preoccupation. The Kobudo Shinkokai (society to preserve kobudo) was only established in 1935, because the older ryu were 'already,' at that time, largely abandoned.
3. Again - what Hirai seems to state is that Aikido was a basket term for all grappling based arts that were not judo within the Nippon Butokukai. But as I wrote below, that may not have been the case at all.
4. Hirai's position within Ueshiba's organization is actually rather odd. He was the general manager of the dojo/organization, yet he maintains that he was separate, that he'd created his own martial art from his variety of studies - that, nonetheless, really looks a lot like aikido. Parallel evolution? Why, in fact, is it called Korindo Aikido, which is sort of like Kendo Iaido or Judo Karatedo. Yet I've never seen anything, even obliquely, from the Aikikai that criticized or questioned Korindo.
5. Anyway, the only way to get an answer to this is contacting someone who is plugged in to the prewar history of the Butokukai. I will make an attempt and get back.