I've never found an answer to this either, but doesn't it seem like the whole thing was staged? Just a power move. If Bill would have just dropped his pants and thought it was the greatest thing ever to happen to him, he wouldn't have been in the situation to begin with.
On a related note, Make SURE you have your subtitles turned on during the scene in the costume shop with Leelee Sobieski. I think this is one of the most important scenes in this movie.