I haven't seen the complete Alien Evolution documentary, but the one on the DVD is rather different from the Alien Saga piece. Alien Saga goes through all four movies while Alien Evolution's focus is more on the original Alien and its impact (if I recall corrently, they interview everyday people for their reactions to the chestburster scene). With only about 10 minutes cut from the Evolution doc on the DVD, I doubt it went much into the other films.