chan wing yan's character development

Am I the only person who has difficulty accepting that Yan is the same character played by Shawn Yue in this film and Tony Leung in the others? Their personalities just seem too different to be one person. Yue was brooding and angry while Leung was a bit more sarcastic and witty. Not only that but they don't look or sound alike in the least bit. I guess you could argue that when Yan was just more troubled as a young man but eventually got the hang of being a Triad and maybe even enjoyed it at times. But I just don't buy the sudden character change. Do you feel the same way?