what-if Tohei only understood a small aspect of the one-point?
*put on asbestos underwear, going to be hot here soon*
Off topic, but it's a moot point. Just as Ueshiba gave the nod to Tomiki, Shioda, etc, he also gave the nod to Tohei. It's aikido.
IMO, just as Ueshiba looked at his peers and saw that they were making the way of aiki their own personal way, so, too, did Ueshiba look at his students. I think Ueshiba understood that aiki requires a personal approach in which to display those skills.
Historically, Tohei went elsewhere to start learning these skills and so far, that seems to have been okay with Ueshiba. Shioda went to the Kodokai and so far, that seems to have been okay with Ueshiba.
If you're studying a system designed by Tohei and you're using aiki, it's aikido. If you're studying a system designed by Shioda and you're using aiki, it's aikido. Etc, etc, etc.
What Tohei's understanding about One Point, etc really doesn't matter to me. It would if I were learning from Tohei, but I'm not. If you started training in that system and started learning aiki and you take it as far as you can go ... well, hopefully, you'll surpass your teacher. Isn't that the plan anyway? If you have to get outside help, well, that wasn't exactly frowned upon by the founder either, as far as I can tell.