There also is a diode that is used in separation. It is located in the fuse box. Looks like a two pin relay, about the size of the later spade type fuses.
US cars also allow the seats to be adjusted without the key when the doors are open. The difference isthe windows and sun roof. FWIW, part of the DOT conversion that was supposed to be done on that car required neutering those functions. The wat that was done often causes long term problems.
If you live around MBs long enough you can come across some real ironies. When my wife bought her US-BUILT ML320 I was dismayed to find that seat function was removed. The key now had to be turned on to move the seat which was a PITA when my wife has the seat all the way forward and I am going to drive. I lived with it.
A couple years go by and I am exploring and I find that the ability to control the seats without the key on IS a programmable function of the AAM (all activities module). BUT, BUT, it is emphatically stated that this is not to be done. So I did it, and I found out why. The dumkaufs produced a car in the US with only european style controls; the windows and the sunroof are thus also activated and little Bobby can now chop off little Jill's head with the door open and the key off.
Bosch Master, ASE Master, L1
33 years MB technician