Many, many moons ago when I was flying for Transamerica we had a contract with Saudia and we always used such a system with our B747-200F.
I think it was in Riyadh (but it could have been Dahran). We used to taxi up to the terminal then were towed the remaining distance where the nose was inside the terminal. Nose was opened and the floor of the cargo system then rose and extended to connect with the aircraft. ULDs then rolled out of the aircraft, direct into the cargo system.
Very impressive it was in the day.