Re: Yoshinkan Basic Stance
The best explanation I have heard came from Inoue sensei, when I met him a few years ago. He was talking about the characteristic rigidity of Yoshinkan aikido rather than the stance, but I see the stance as just another aspect of this. He said that the idea is to start rigid as a way to teach correct shapes and angles to beginners. From there, the idea is to get softer and softer as you progress. I think, similarly with the stance, you want to eventually move into something closer to shinzentai, but it can help beginners to come to grips with the correct shapes if they start in an exaggerated and stylised stance.
I also read an interview with Inoue sensei, where he said that the rigidity, counting, and exaggerated movements of Yoshinkan were developed for teaching large groups of people, such as in the armed forces, where the teacher did not have the freedom to engage with each student individually, so everything had to be exaggerated for the students to get any understanding of what was happening. This also makes sense to me.