If after 15 years you haven't figured out what the guy in the story is talking about, why is this anecdote an argument for anything at all (other than "Don't worry too much; your interviewer might be a nut and shoot you down for no reason.")?

Many people, when this sort of topic comes up, claim the bottom line is that it never hurts to err on the side of dressiness, but this only makes sense if you take 'dressing up' to be a near-universal social code. A clothing rule that can escape being used or mentioned within your hearing for 15 years of life in a culture is almost by definition not part of any universal code.