That same 747 had flown non-stop from Athens to New York that day. By comparison a flight from New York to Paris was a short hop and there is no reason why the center fuel tank should have been filled.
Your argument is incorrect. The distance from Athens to New York is approximately 4,900 miles. The distance from New York to Paris is 3,600 miles, which in comparison to the New York-Athens distance is in no sense "a short hop". The only short hop would be the 1,300 mile one from Athens to Paris.
My point is that the flight to Paris was only 3/4ths as long as the flight the aircraft had completed earlier in the day so it isn't surprising that they didn't fill all the fuel tanks.