I don't know, but I don't think that they're all 100% insanly flexible like Takahashi and the original S/mileage girls. If being able to do the Y-balance was a normal thing, why would it be considered a special talent by certain girls?
nah, I just thought one should be quite flexible to do the Y-balance thing. It was the first thing that came to my mind when I thought of showing flexibility that's all.