One thing I don't think is properly mentioned (?) is the ACTUAL operational records of the fuel pumps. Yes, they were tested afterwards and considered capable of working at full capacity, however, I PRESUME that they are variable speed, so would the speed that they were ordered to work at and that they actually worked at be recorded anywhere ?
unless there was a problem with both gearboxes the speed of rotation of the input shaft to the pump is fixed to the speed of N2(3?) and therefore known.