Al R, it all depends on the aerodynamics.
Certainly fuel pooling on the bottom of the bombbay doors, ie the join, will either seep out or flow out if the doors are open. Where it goes after that would be a guess. It would be quite possible for it to flow up the fuselage within the boundary layer.
With the doors open the inside surfaces of the doors would propbably get a good airing. The bombbay itself and it cabin floor may be untouched by the airflow. Where the additional air flow drives the fuel however would be unknown.
May be there has been an assessment and a decision that opening the doors may cause more problems than they solve.