I think we're getting there then!
So bonding seems to be the really the important part as far as refueling is concerned so that no discrepancy in charge causes electricity to leap from pump to aircraft or vice versa.
And if the thing you're bonded to is also ground based, i.e. a self-service pump, you're also grounded (and I imagine said thing is a lot less likely to have any charge of its own built up).
But if you're bonded to say a fuel truck, perhaps you're less 'grounded' due to the poor conductivity of the tires.
Then again maybe fuel trucks also have the rubber conductor strip that was mentioned as being present on some older cars.