I saw an interview with either John or Clint several years ago when that question came up and that was the gist of it - though my recollection was that Clint said he was supposed to say " it's a special light load" instead of " a light Special load" and he got the line backwards - no one paid much attention to it at the time and filming proceeded. Like I said, that's one myth that the "experts" will never let die . . . . besides, the context was for a competition shoot - not what he was carrying on the street.