Again I would suggest you go back and read what Tohei actually said about what he got and from whom.
You can continue to repeat your view that he found it and developed it under Ueshiba's watchful eye. Lord knows you will find many who will agree with you. I think you would find it worthwhile to check in with what the man said and see how that aligns with your opinions of where he got it from.
I'm familiar with his AJ interviews and his claim that Ueshiba really only taught him 'how to relax", but I also know the lengths the man went to distance himself from the Ueshiba side of the art following the split. He was scorned, and rightfully so, so it's hard to take a comment like that all that seriously considering everything involved. Considering all the bad blood I don't think it's a stretch to think that.
The early 1961-ish books he put out and videos were all done with Ueshiba's approval and they all contain the taiso. In addition to that, you can see plenty of vids of Ueshiba doing things like funekogi, furitama and other things that contained movements that became the taiso. While Tohei obviously got things elsewhere too, the bouncing ball of logic tends to support that he got things from Ueshiba too.
Go a step further and factor in that he was the chosen son for a long time. Ueshiba obviously approved of what he was doing enough to let him put out books and videos with all of this stuff representing HIS art.