several hundred years after the original Zhouyi core text. The writers of these texts don't necessarily have had the same understandings as the original writers, and had some entirely different views. Their focus on proper conduct doesn't quite fit with the more spiritual Zhouyi. What they wrote thus cannot be taken to be authoritatively illuminating the Zhouyi.
Many people take Wilhelm's, or the English translation by Cary Baynes of his Yijing (which was originally in German) to be the "best" translation around. The language that Wilhelm uses, which is inspired by Goethe's, certainly gives the text an aura of mysticism and authenticity, which may impress people. It has become quite popular, especially as it was the first Yijing text that gained widespread use in the West.
But it doesn't mean that his translation is to be considered accurate. Many parts of the translation are debatable. Furthermore, Baynes' English translation does contain some remarkable translation decisions, like translating the German "der Edle" with "the superior man," instead of the more direct "the noble" or "the noble one." These words have some very different connotations.
Wilhelm's text is based on a Confucian interpretation of the Yijing. As described above, I consider this approach inconsistent with the core text of the Yi.