He doesn't answer the 'why' but there's an implication that the printing shop had orders to produce X number of one time pads and it was half the work to setup

He doesn't answer the 'why' but there's an implication that the printing shop had orders to produce X number of one time pads and it was half the work to setup the apparatus this way. Basically it was a shortcut that presumably felt entirely reasonable to folks running the printing press. And maybe even technically compliant with their instructions depending on the wording thereof.