As you well know BA doesn't have a requirement to carry out a dupe for closure or to function the t/r post c-duct closure. I can only assume this is because the amount of people required to actually close them with respect to the older 'c' engined powered a/c would far exceed the usefullness of a dupe less the extra certification stamp.
I suppose it would be quite difficult to dispatch one of these a/c with the c-ducts unlatched baring in mind the baulk design of the hinged doors covering the latches.
Having said that it was probably never imagined that a certain roll-on roll-off car ferry would ever be allowed to leave port with its bow doors open.