I understand, very 3rd hand, that a young man was offered the FO position on the 604 based at Essendon. He, for reasons unknown, had wanted a seat on the Dash 8 so he requested that. Was told that those positions were filled and therefore unavailable. When he then said, oh well the 604 it is, he was told that as he had expressed a wish for something else he was no longer acceptable for the 604 and therefore was rejected.