Once again, hindsight. He's speaking from the perspective of NOW, not 27 years ago when ANH first came out. For all we know, stormtroopers bumping their heads in the OT could have been a happy accident that he decided to leave in @ the time, but now he's going back and trying to give that accident meaning. He may do the same thing with some of Harrison Ford's improvised lines in the Indiana Jones trilogy for Indiana Jones 4.