I would be pleased to have some comments on this scenario:
Before reaching the end of the CT, some of its fuel might have been frozen due to the small quantity, inhibiting both boost pumps due to the LOW PRESS condition. If for some reason the crew didn't manually switch off the pumps, the frozen fuel from the main tank may have melt during the descent, causing the boost pumps to restart, feeding both engines with the slush from the center tank.