GPS Proves Special Relativity?

Reference is often made to the Global Positioning System (GPS) as evidence for theories of relativity.  But does GPS prove or disprove Special Relativity?

What the Global Positioning System Tells Us about the Twin's Paradox

Today, many physicists and students of physics have acquired the impression that these two [Special Relativity] postulates have been confirmed by observations. However, that is not the case. In fact, none of the eleven independent experiments verifying some aspect of SR [1] is able to verify either postulate.

The Speed of Gravity: Why Einstein Was Wrong and Newton Was Right

It may surprise you, but the GPS system doesn’t actually use Einstein’s field equations.

The fact that the Earth is not accelerating toward the visible location of the Sun, but rather 20 arc seconds in front of the visible Sun (where the Sun will visibly be 8.3 minutes in the future) is very strong evidence against gravity propagating at the speed of light.