I think that’s highly debatable. For example, dark matter particles with testable properties could be a prediction of a ToE. Or the ToE could resolve the quantum measurement problem (collapse of the wave function) in a testable way.
AFAIK an EoT is not required to design experiments to determine if it's a real physical phenomenon vs. a mathematical trick; people are trying to think up those experiments now (at least for hidden variable models of QM).