I see waht you're saying, but both my C wagos and may GLK if the driver's door was closed and any or every other were open I was able to lock them all. one they were closed.Mercedes has always been very very cautious about locking keys in the car. Even way back in the 70s they had a mechanism that prevented you from locking the drivers door if it wasn’t shut- couldn’t push down the plunger, couldn’t lock it with the key. I assume that’s a related concept.
As last my as I remember, they have also been immune to slim Jim’s