To return to the question, the reason for the delay may well be along the same lines as the B747s. They have a cam actuated system to unlock the doors then the gear uplocks in the alternate mode and the cam takes about 90 sec nose, 30 sec mains (I think) to complete a cycle, hence the requirement to leave the switch in "arm" for a time. If the cycle is interrupted, there will be problems later with gear door sequencing etc.