For example, you can see many photos where Ueshiba, within aikido technique, replicates this in-yo with his body, in various configurations. On page 45 of HIPS, there is a picture of Hisa Takuma doing a dramatic version of the same thing. Let me suggest the possibility that the assiduous student would try to create this structure in every aikido technique - not primarily between uke and nage, but within oneself.
I'm unclear how Ueshiba is doing anything particularly different than in most other art that use jin/kokyu and qi/ki skills. The important thing is differentiating Open and Close and what people are calling "winding" is really just a variation of the Yin-Yang formation of Open/Close. Maybe people should clarify (go into greater detail) about what it is that they think Ueshiba is doing.
The picture of Ueshiba with the Open-Close (Yin Yang) is interesting, but wouldn't be significantly different than a lot of the common symbolism of the earlier times. For instance, if you take that fist and place it within the flattened other hand, you have the famous and common Sun-Moon symbol (indicating Yin-Yang) that was and is commonly used by martial-artists in China.
My point being that I'm not seeing Ueshiba do anything that makes me think "oh, that's extraordinary and it's being done is a way not explained by common internal-strength theory". Maybe I'm missing something? Or maybe others are missing something. It could be an interesting discussion.