I don't think you even have to say you're "fatigued." Simply say you chose not extend beyond the CCO that came off the printer. It's a harassment factor the company has inserted to get the pay you're owed because they didn't like being told they had to get the pilot's permission to extend. They hate being told what they can and can't do.

If on reserve and you've got no chance of breaking guarantee you don't even have to file an FSAP since it'll make no difference in your pay.

BTW, It's a misuse of the FSAP system IMO. FSAP is meant to be for safety issues and they're using it to get us to grovel for pay. I wonder what the FAA rep on the FRC thinks of reviewing FSAPs for pay.