Volume and mass
I was intrigued by the discrepancy between planned and actual arrival fuel.
Fuel tanks measure volume (albeit it is displayed as mass on the gauges).
Pumps supply volumes.
Engines produce power depending on the mass of fuel.
If the density of the fuel had changed during flight - it may be of sufficiently low density that even with the pumps operating at full volume - the mass of fuel presented to the engine was insufficient to produce the required power.
I am not a chemist, just a retired driver airframes, is it possible that a gas (air) could have been mixed with the fuel to lower the density during flight?
This may explain the apparent fuel discrepancy.
There are many variables that affect fuel usage on long sectors but, with several thousand hours on longhaul (DC10) aircraft, I was suprised to find the aircraft made that much fuel.
I will also say that I think everyone who criticises the crew have the benefit of hindsight and I think I wouldn't have done much different to them.
I have flown several times with the captain when he was a co-pilot and he is one of the better guys!!!