I couldn't see it touched on in the article, maybe it was and it went over my head, but it seemed to only address this comment in a dry literary sense.
But in my own training, unrelated to aikido, we have at one point used sounds to coordinate 'things' in the body that are hard to coordinate or make move by any other means. These particular sounds not being the pair of 'A' and 'O', but something else, though 'A' was conspicuously present, in a form, and maybe even 'O', if I look past the superficial sound itself.
Though the sounds were not what was sought after, and other sounds could have been used in the end, or really no sound (which was sought after), but the sounds were a gateway into that state, to identity what unconscious effects they had on the organization of the body first, then make them conscious, then get rid of the sounds and keep the effect. The sounds are like postures, ends of a spectrum, for some aspects the body, but in between the sounds, there is movement, of a sort, and that is what you try to learn.
I haven't really touched on that, since I've been trying to keep things clear and (mostly) understandable.
Of course, that's the whole paradigm of Kototama, and the chanting that Ueshiba did was used for that purpose. Basically speaking, I think that he was using it to focus his intent in certain ways, and this worked well for him because of his religious beliefs and background.
For other people, perhaps not so much (it never did much for me). Notably, he discouraged people from joining his religion or joining in his religious exercises, so maybe he understood that it was different for his students than it was for him.