I've never tried opening it when driving either, although rightly or wrongly I long ago stopped switching the engine off when fuelling. I figure if modern tires conduct well enough to conduct lightning they conduct well enough to dissipate static (even if the engine wasn't running and they didn't it would spark on the pump nozzle and kaboom!) and engine heat is too far away to worry about.
Switching the ign off while refueling is no so much about causing a fire but it messes with the evap control system. I have even seen the check engine light come on after refueling with engine on.