A more appropriate analogy would be one where a customer booked a first class award ticket. After completing the reservation, the airline sends an email that if you miss your flight for any reason, you would be charged the full cash price of a last minute ticket and you miles would be refunded.

Ex.: Customer buys a first class ticket form JFK to HKG on Cathay Pacific for 70K miles. Because all flights were cancelled from her departure airport, she asks calls the airline to explain that she will miss her award flight. The miles are refunded she is charged $20,000, even if the airline resold the seat. Even if that is legally permissible, I would avoid booking an award ticket with that airline.