FE in its need to explain the problem that Newtonian (or Einsteinian) gravity would mean mean that you'd weigh more in the center of the FE than elsewhere (and that is not observed) decided to through real gravity and invent its own. Relying of the EP and ignoring the Cavendish results, FE decided to have an unknown, unseen, not predicted, and non-falsifiable Universal Accelerator provide a poor mimic of gravity.
You need only say Cavendish, g varies with height regardless of the stars overhead at the time, or gravity on Earth is radial and tidal to dispel their UA and their theory. Unfortunately they did manage to obscure their failing from those not well-versed in EP. Even today lesser educated (Note this is no way is meant to impugn anyone's intelligence!) REers are tripped up by how they use the EP successfully. (Marbles in dough for dinner, anyone?)