(It causes me to ponder the control linkage arrangement!)
The control links go through the hinges. I bet it was complicated to design hydraulic cables rugged and reliable enough to withstand the tail door opening and closing thousands of times.
I read somewhere that the hinges used on the Dreamlifter tail cargo door was derived from the hinges deveoloped for folding the wingtips of the 777. No airline has opted for the folding wings due to the weight penalties and work arounds to get planes to fit in to gates.