You are not wrong here. The solenoids were indeed 'switched polarity' as you call it (no idea what the proper name is though). Two wires, either RK/RS (+12V/Gnd) pulse for lock, or RK/RS reversed (GND/+12V) pulse for unlock. The lock module takes care of it.
However, for the lock module to see if the door is locked or unlocked, the module checks the state of the locks by checking the switch sensor. This sensor is connected through 3 wires: GND, NS (Brown/Slate) and NK (Brown/Pink). If GND connects to NS, the door is locked, if GND connects to NK the door is unlocked (or vice versa).
Now, with my $10 central locking module, the basic +/- logic is maintained (therefore it works for ALEXANDROS), but the actuators also senses which way the lock is being pulled (either by the exterior lock, or the interior switch). The fact that it senses a DIRECTION and not a STATE is why the original lock module is not compatible. Another reason for it being incompatible is the power required for the actuator to move compared to the solenoid (i'm not sure about this though). Anyway, my new $10 lock module has a remote which is of course very cool. Installation will be pretty easy since the PO already exchanged the solenoids for actuators. My new $10 lock module has 2 bonuses. 1) it can be configured to close the windows automatically on lock, and 2) it blinks the direction indicators when locked/unlocked.
I tried to explain this as comprehensible as possible. If it is still unclear, let me know.