If you change fuel height in the aircraft configuration menu to 3.41 the fuel hydrant truck will come to refuel.
Yes but, in order to not seeing the fuel cable sticking out of the wing on the top side, the refueling position should have to be moved quite a bit towards the exterior too.
We decided to place it in its real position (even if it meant not having the Hydrant and we WILL eventually have a different animation for lower airplanes), but the whole point of being able to customize an airplane in GSX, is that users can always choose to bend realism a bit, if required.