Yes, the thought of fuel/air mix and sparking pumps does not fill me with joy! I believe this is the reasoning behind the Boeing restrictions.
However, if the AB restrictions apply because of the torque of screws/bolts, why can you put some fuel in the centre tank (A320/319 - >2000kg, IIRC) - and that's ok but when you get lower than this - the fuel becomes 'un-useable' and the pumps must be switched off???
This seems strange - or is it that if the torque on the pump screws/bolts is less than ideal, then this could lead to sparking/fire/explosion. (Above 2000 kg, the pumps would be definitely covered in fuel, any less and the pumps may become uncovered, coming into contact with the ullage (fuel air mixture))?
Whatever the reason, I don't quite follow the logic of AB - we've just been given a temp procedure but without any adequate (IMO) explanation as to why.