I have come to the conclusion that they are in fact broken as they stand. Yes on the breadboard they are not useful, but as but one counter example the PI zero (or any of the other PI parts and many other mcu boards) uses proper dual row headers (probably made internally from 2 singles I will agree) profitably. It looks like the real board looks and you can run wires to it from either the breadboard or probably more usefully other modules. We should fix the current implementation to be able to generate proper (and thus properly connector numbered which is the pain with two single headers) parts for breadboard to make generating a part like the PI easier, at least in my view.
Peter