Discretion is the Captain's responsibility.
The problem is if you have a cabin crewmember on board who wants to stick with his industrial limits which might be more restrictive than the Captain's discretion limits.
In which case Bassa will almost always tell the crewmember not to operate, and the union will tell cabin crew ops that the crew are out of hours and the flight will not go (unless a second crew can be found).
So Bassa run the operation and there's virtually nothing the Captain can do.
This is what WW wants to change, and Bassa don't like it one bit. (See Bassa's briefing to the city above.)