In English gunmaking screws are meant for wood, pins are screws that screw into metal and axles are threadless pins.
From the engineering point of view, axles are prefrable to pins (screws in the US) since the threads can act as stress points. They are also easier to get them right and easier to replace if necesary.
However, screws are regarded as a quality feature and some gunmakers insist on using them on higher grade guns. I had a long talk with my Italian maker re axles on my boxlock. He nodded like he understood, the gun was eventually delivered with pins (screws) and locking screws. He told me that there was no way one of his best guns would be made with axles. It is a pain to disassemble since the pins (screws) have the typical small Italian style slots and are engraved.
I guess the maker's approach in the two OUs was similar to my Italian maker's.
