While it is certainly safe to say that the Yi Jing (I Ching) influenced both Daoism and Confucianism, it was not the origin of either of them. After all, there are many aspects of Confucian and Daoist thought that cannot be traced back to the Yi Jing. But perhaps this is all simply a phrasing problem! I haven't read The Way of Zen, so I'm not exactly sure how Alan Watts makes this particular argument about the Yi Jing.

I'm sorry for giving you such a brief response. If you'd be willing to type up a very quick summary of Alan Watts' argument, I'd be happy to address it in greater detail.