As told to me by an engineer, the advantage of the CFM cowl is that, unlike the V2500, the latches can only be closed flush when the doors are closed. Therefore an unlocked door must, by design, have its catches protruding. On the V2500, the latches can be closed whatever the position of the door. Indeed it is (was?) common practice to close the latches on opened V2500 doors to avoid walk-by injuries. Thus the CFM should be much easier to check on the pre-flight walk round.