I'm currently playing with a system that has a 24V DC control panel and every relay has A1 connected to 0V.
Not really a problem currently, but a few years back I took out a channel of a dedicated control unit when thoughtlessly adding a diode quenched relay to a digital output through connecting A2 as per drawing. i.e to the digital output of the controller.
The control panel wiring in that was 24V too, although the panel builders had obviously not wired to the "as builts", which showed every A1 grounded.
The damaged controller was got around with the aid of a software Engineer back home who managed to nominate a spare i/o, but since then I have been very wary of the consequences.
Does A1/2 misidentification cause problems generally? is it common to ignore polarity in systems with "unquenched" relay's?