Just for info , we receive the same kind of memo here ( the little sister company across the airport ) to remind all the cabin crew that it was captain discretion , only making them believing that the captain could decide if the crew was fit or not to fly!!!
This is a " convenient " interpretation of the captain discretion.
The captain is supposed to ask all the crew member if they are fit to fly into discretion BUT can not decide for them or worse force them to fly.