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When you turn an electromagnet to the ON position, a magnetic field suddenly covers a new area that in the past it did not cover (as in, when the switch was OFF).

It is *valid* to inquire as to how fast that field covered the new area.

But there's no physical way to do that with a gravitational field. Furthermore, the sun's field has been "on" for billions of years. Furthermore, there's no region of space that is not permeated by gravitational fields. Anything else you can talk about is propagated in the form of waves, as you have admitted, and regardless of what nonsense you believe about switching things on (as if any point in space has more than one vector potential). And also as you have admitted, those waves propagate at c. Nothing more has to be said.

The Einstein field equations give accurate and verified results for any physical situation we've had the opportunity to measure, and without postulating any velocities of the kind Van Flandern imagines. They are utterly superfluous to the theory. As Laplace told Napoleon, "I have no need of that hypothesis."

"But there's no physical way to do that with a gravitational field."

Are you saying that we can't measure the difference between the angle at which the Sun's Gravity pulls the Earth and compare that angle to the angle at which Light finally reaches the Earth from the Sun?

They are utterly superfluous to the theory. As Laplace told Napoleon, "I have no need of that hypothesis."

That was when Laplace showed Napoleon his treatise on celestial mechanics, Napoleon asked him what place X had in his theory. Laplace replied that he had no need for that hypothesis.