Oh, that's been like that since Tekken 1. Lee Chaolan was adopted by Heihachi Mishima at a young age (approx 8-10 years old) to provide competition for his biological son Kazuya as Heihachi thought of him as weak and in need of real challenges. By getting a street kid who was completely loyal to him as he percieves him as a savior Heihachi hoped to breed a fierce need for approval in Kazuya to outdo his brother who Heihachi made his favorite son. Instead it just made even more people who want Heihachi dead as they both rightfully resented him. He's not really good at the whole "planning ahead" thing. It's always been like that :-|
he is from it. actually now that i remember he has arms as well.
actually i did see a piece of concept art with songbird where they had the diea that he held onto his wings and flapped his arms, somewhat like how people thought one COULD fly back then. either they decided her would not be as great a threat if he had his arms restrained doing so, or thought that making his wings operate seperate from his arms would give him a visage somewhat like a guardian angel, a warped steam punk gimp guardian angel, i do not know, but those are my theories there.