I think I understand, but then they owe you another one, and it counts against the 10 qualifying events per calendar year. If you give them 5 choices, (or less than 5 if there are not 5 days that comply with their requirements) they have to pick one. It cannot be waived by the company unless you take the premium pay for the day off you worked. Actually, you have a good argument to tell them to pound sand; it's a protected day, more so than just a regular day off.

Speaking of shenanigans, don't accept trips that have scheduled duty periods over 12 hours, unless it's the +1 hour to DH to domicile. If you notice it after the fact, call them on it: they have to modify it.

Our contract, such as it is, is a collective bargaining agreement not an individual contract of employment. We are employees, not contractors. Think about that when you are pressured to waive the contract or consider waiving the contract.

Be polite, be considerate, and ensure the company follows the law.