im going to guess this was done because of the new movie. It's done to ease a similar plot element in the new movie.
I havent read the whole thread but did anyone make this joke, already?
New Alien prequel!
Kane's Son, an evil alien, was killing the crew of the Nostromo when the good alien, Big Chap, came in and stopped him.
He got tired and was having a bit of a lie-down but Ripley confused Big Chap with Kane's Son and killed him.