That's exactly the approach another smaller Irish carrier* based in Swords took recently; call up crew, ask them what they're going to do, make a note of it and dick around with their rosters if they didn't parrot the company line or answer their phone.
Entertainingly, nothing happened if a crew member had told the manager concerned what they wanted to hear and then "changed their mind". Their manager was probably just calling them because (s)he'd been instructed to and had to have known what was going on, but provided (s)he could tick the box (s)he could move on.
So, lying => bad; changing your mind following a telephone call => fine.
Bonus entertainment value was that it screwed with management plans.
*whose name rhymes with easyjet.