"The matter" in that quote is the matter of whether the Earth orbits the sun or vice versa. Naturally there's observable physical reality to distances and whatn

"The matter" in that quote is the matter of whether the Earth orbits the sun or vice versa. Naturally there's observable physical reality to distances and whatnot, but if you use the laws of physics to make predictions about those observables, the math works regardless of which body you assume the others revolve around.