Well Dave, I sure hate to bust your bubble, but in this case I am right, you are wrong.
There are 3 bulb sockets in the harness, a black one, an orange one and a gray one.
The black one is obviously for the tail/stop light as it has 2 bulb connectors, the other 2 only have one.
THE BLACK WIRE RUNS FROM PIN 1 OF THE HARNESS CONNECTOR TO ALL 3 BULB SOCKETS AND MY TRUSTY METER SHOWS IT IS CONNECTED TO THE BULB SHELLS IN ALL 3 SOCKETS.
Guess the Germans just wanted to mess with the DIN standards people on this.

( power DOES go to the bottom contacts on all bulbs, the brown wire is the power wire for the gray socket )