Yes fair enough, if the sensor arm is in a valid, but wrong, position the system won't know.
I was thinking back to when my front arms were changed to M3 items and we had to wait for the M3 levelling linkage to arrive, the garage unplugged the levelling sensor, so the system put the lights into safety dip.
If a rear linkage is disconnected, the weight will pull the sensor arm DOWN which will give the impression the rear is UP (i.e. nose down) and the car wil raise the headlights.
If a front linage is off, it will think the front is UP i.e. nose UP, and it will lower the lights.?
OP - still needs looking at!