The fix to the GSX settings eliminated the constant unrequested fueling.
Note that, by default it's disabled so, it's possible you might have enabled it, maybe long ago, without recalling it.
I don't think that an actual simulated filling of the different tanks is really necessary and most probably would be way too complex
We never tried to do this: the only airplanes that GSX actually refuels, are those using default fuel system (those flagged as such in the airplane customization page), but the ones using their own fuel loading system, like PMDG, Aerosoft, FS Labs, GSX don't touch *anything*, it only reacts to fuel changes happening in the airplane but, in order for this to be working, the airplane should at least use only the standard fuel tanks variables, that's why I guess the Concorde couldn't be adapted like the PMDG 747, for example, since it has far more tanks than what the default system allows.