it must be because you need to put the repair wire in a different pin. you're right that for the 8P3 the wiring is different, but if you know the pins you can swap them over no bother. your best bet is to ask someone for the pin diagrams off ELSA of the plugs to the headlight switch. once you know that it should be pretty straight forward. compare the two and instead of putting it in pin 12 like the diagram, put it in the new pin - that is of course unless the new CECM doesn't allow it at all.
Argh, you're building encouragement again Sub, stop it
TBH it's very unlikely the Control module would allow it as it seems pretty restricted compared with the 8P2 BCM that I've interacted with, but that's guessing.
I've got the enthusiasm, the time and the budget to try it - just not the skill or experience in terms of electronics
Is the pin diagram going to shed any light at all?