Of course it's unethical.
Tom wanna buy some goods (admission confirmation) from Jack; Jack announced certain criteria and the date to release the results; Tom thinks he might get the goods, therefore he pays the fee (application fee); But during the day to release the results, Jack said, sorry, we can't give your the goods, but you might or might not get it in a few days, it depends upon some other criteria and you have to wait.
It doesn't look ethical to me. I just think it is simple, the waiting list thing is just something that the schools wanna maximize their profit while get rid of any liabilities. And the worse thing is, most of the candidates on the waiting list might still appreciate such list.
It is an interesting topic for research of game theory, strategy and non-linear programming. The difficult part is data collection. Nevertheless, if a system can be developed, it would be much more good to applicants than to schools.