That is certainly true of the far reaches of physics, but the point is that, if it cannot be tested, it is and remains an hypothesis. Science sometimes just describes "what is" rather than "why it is."

There is no Universal Field Theory, but both Quantum Mechanics and Relativity have been tested extensively, and they both work. What they predict will happen, happens. We may never know how they fit together, but that does not make them any less true.

Zelazny has one of his characters say it best: "I bow to the unknown, to the unknowable I bow not."