"The fuel scavenge pumps (powered by pressure from the main tank pumps) then start to transfer the muck to the main tanks."
Note that muck in the CT has to pass through an inlet screen before it is scavenged, then through a narrow opening at the jet pump, then, flowing from the outlet of the jet pump, has to jump over baffles, pass through wing boost pump inlet screens, then has to pass through one or two engine filters (depending on where the blockage is), one of which has an impending bypass alert..... and almost simutaneously affect two engines.
Not saying it couldn't happen, but....
So rough calc suggests the scavenge from the Center to BOTH Main tanks started about half an hour before landing (72,000kg/12 hours = 6,000kg/hr of flight).
The CT fuel scavenge rate is 400Kg/per hour
minimum. By your calculations the centre tank would have 700Kg remaining on landing
