Exactly! Sqeuch, you are identifying the exact reason why the earth strap >>IS<< needed on aircraft. If grounding took place when the nozzle touched the filler neck, there would most likely be a spark, which would ignite the fuel vapour... then KABOOM!
The reason cars don't need bonding straps is because the fuel tanks are insulated from the static in the car body. (in fact most fuel tanks now are of plastic construction).
Also remember AVGAS is far more flammable than Petrol.........
And Petrol is far far far far more flammable than Jet A1............