It is true that Bruce did not finish study of the entire classical Yip Man wing chun system before coming to US. Bruce developed some effective modifications of wing chun that I doubt Hawkins has any experience with. Some of these mods directly oppose and circumvent classical wing chun theory. To my knowledge only a few of Bruce's first students have demonstrated experience of this. A couple key points to remember are that Bruce was mainly interested in winning, and that he was not always open with people (including students) about what he knew how to do.