1500+ hrs on the airplane and didn't notice it as you describe it(center tank related)
Did notice, as on all Boeing fuel/FMC readouts/predictions, that total fuel reads low after climb/level off and FMC prediction is optimistic early in cruise but increases accuracy of predicted arrival fuel later in cruise, which is similar to what you appear to be describing.
IMO the typical discrepancy between early cruise predictions of FMC predicted arrival fuel would be 1000-1500 lbs (450-700kg) optimistic vs. the expected/actual arrival fuel.
Did not appear to be center tank related as it was often, if not typically, empty.