Not trying to speculate but I believe there is a situation on 777 where you can get into trouble by blindly following checklists. A massive fuel leak will lead to low fuel on one side (obviously). After the fuel imbalance checklist, later will come the low fuel check which asks for either crossfeed valve to be opened. This then drains the other tank. Some of my details may not be absolutely precise but have heard of this scenario in the sim.