ISTR that low-fare airlines also often do baggage differently. When the aircraft arrives, the departing bags are driven to the aircraft. The arriving bags are then unloaded. Then the same loaders load the departing bags. When that loading is finished and the aircraft is ready to depart, the arriving bags are then driven to the terminal and put onto the belt. This is one way in which the turnaround time can be kept down: there is only one round-trip for the baggage train between the terminal and the aircraft.

Imagine the complaints about late-delivered bags if BA were to do this on routine basis.