Kousaku Yokota, writing in Shotokan Myths, points out on page 165, that:
- All styles of karate do some form of hangetsu (seisan) kata. It is the one kata they all share.
- Shotokan is the only style that uses hangetsu dachi, in this or any other kata.
Yokota's conclusion, reached after several pages of unsupported speculation, is that Shotokan needed an inward-tension stance, but Funakoshi didn't like short stances, so he made up hangetsu dachi.
It might just be that the long stance looked good in kata competitions. Certainly it was never an Okinawan combat stance. It's a dance move.
