Faraday's cage has nothing to do with this, that one is about blocking High Frequency signals such as radio or transponder transmissions.
But "ground" and "earth" are indeed used interchangeably. For this once I will disregard semantics
to state the essential: the airplane and the fuel pump must be at the same potential.
BTW the aircraft's 12V= or 24V= have nothing to do with it either: the danger is in static build-up.