The only ethics in business are those enforced by the state. Is it unethical for the state to ask a salaried employee to work more hours? No, it isn't, so I see no difference here. The exact same principle applies equally in both cases. Hours are meaningless if he's salaried. I think it'd actually be unethical to himself if he told on himself to his employer. Our first ethical duty, after all, is to ourselves.