My recent experience is that only the first 90 cabin bags can be stowed in the overhead lockers and under the seat in front of you. That is pointed out in their T&Cs and that's often why folk start queuing well in advance in the 'Other (ie non Priority) Queue'. However, when a flight is full, gate staff pass through the queue and invite passengers to give up their hand baggage and put it into the hold free of charge. It then is loaded as the passenger boards and is reclaimed in the normal manner after immigration/border control at the arrival airport with the rest of the hold or checked baggage.