This rule -- The Obligatory Wait -- about how long Fresno State students are expected to wait (based on the academic rank of the instructor) is famous enough for Jan Harold Brunvand to document in one of his books or urban legends, The Baby Train.
You probably know the punchline: there is no such rule :)
One question that seems to puzzle all new college freshmen is "How long are students expected to wait for a tardy professor?" Fortunately, most of the more-experienced students are ready with an answer. Unfortunately, their answers vary wildly, and most of them are wrong.Also interesting, "The Myth of the Lazy Professor" from the Chronicle.