Let me try and get this straight.
NATS have to save money but still reduce delays so they don't get fined.
You give a bunch of people unpaid leave to save cash. So you run short-staffed, flow control introduced to protect those left and the delays go up. So NATS loses money on the fines.
Or you pay people to come in on AAVCs to keep the delays down which costs the company more than having the people in in the first place.
Something a bit odd here I think.