No Erol.
If they were running 6 and you started in the second car in the loading station, you would be the second in the offload. If they were moving in pairs like you say, they would stay in the pairs. However, the second train in pair A was waiting for the first train in pair B to come back, and they were then going forward to off-load together. Then, the second train in pair B waited for the first in pair C etc.
So, the system may be designed to run in pairs, but on Tuesday it WASN'T. This swap happened every time. Thus, they MUST have been running an odd number of trains, and what you were told is in fact, impossible.