I have recently read many articles regarding Wing Chun history. I found many differences in the history of the Yipman lineage. we all know master Leung Bik, which was the son of the king of Wing Chun (Dr. Leung Jan). This master was yipman's second teacher when he moved to HK for studying.
Leung Bik history is not really confirmed by many people. But I believe he existed, because Yipman's Wing Chun really has changed from hard to soft after returning back to Fatshan, and that concludes that he learned a different concept from a different master. According to what I read about the master history, it was said that his father Leung Jan taught him the real Wing Chun alongside with his borther Leung Chun, while he taught master Chan Wah Shun some different kind of more hard style. Chan Wah Shun was more of a gifted fighter that depended more in his strength to win battle, and that was due to his big body that helped him.
In a history narrated by William Cheung was different. He said that after Leung Jan's death, Chan Wah Shun fought against Leung Jan's sons and defeated them to send them out from Fatshan so he could claim Wing Chun for himself, well that's a strange story?.
Also regarding the encounter Yipman had with Leung Bik as the challenge fight, William Cheung said that it took place in a small boat where Yipman was down several times in the water, while other Sifus stated that he fought against him in a backyard owned by Yipman's friend family in which owned a factorry where Leung Bik worked.
I wonder why the history is not that clear?, I think that we must really care about knowing such things, because without history, you cannot know the past, and if you don't know your past, you can never predict the future.