...because the two meanings have different etymology? And are listed as two separate words in dictionaries instead of two meanings of the same word? Guess it depends whether you're defining a Janus word by lexical meaning alone or real life usage. Is it the form or the accident? Does the form have a life of its own apart from its accident? Or when used in real life is it the same spelling so effectively and to all practical purposes the same word with a different meaning?

This also raises the question of whether words with the same spelling but different pronunciations qualify.