With fuel tank truck I guess. When I was in the Air Force we had a "button pusher" guy playing with controls in the cockpit that he knew nothing about and set the switches to dump fuel. When someone later applied power to the airplane, it proceeded to dump 12,000 lbs. of JP-4 onto the tarmac.
A weight-on-wheels switch should prevent that. Maybe it was disabled for maintenance or testing. There’s always one guy who will mess around with things and has no idea what he’s doing.