That seems a little silly to me. Should I custom make the drone with four propellers, or four? Should I have a camera, or a camera? Should I have the most appropriate battery, or the most appropriate one?
The cool thing isn't the number of propellers, but that they can change the model and produce a new drone on board. The alternative is to either get it delivered somehow, or return to a port to pick up the new drone.
3D printing will save them lots of time if they choose to change the design. Also, spare parts can be produced on board the ship.