Corruption of Modern Physics 8: Equivalence Principle

In Dialogue Concerning the Two Chief World Systems Galileo lets Salviato explain to Simplicius why different bodies with different masses show the same free fall (in vacuum without air resistance) thus with the same acceleration subject to a gravitational force, in other words that inertial mass scaling with  acceleration is the same as gravitational mass scaling with gravitational force. 

Galileo demonstrated this fact by dropping different objects from the Tower of Pisa. Galileo argued that this must be so because if different parts of a body in free fall would fall differently, bodies would be ripped apart by internal forces and the World could not exist. This is called Galileo's Equivalence Principle and is a cornerstone of Newtonian Mechanics. It says that there is only one type of mass, namely inertial mass, which manifests itself as force resistance to acceleration expressed by Newton's 2nd Law.  If you want to find the mass of a body, measure the force required to put it into motion.  

It is now reported from Institute of Theoretical Physics, University of Paris-Saclay, France, that 
the 

• MICROSCOPE Satellite Experiment has tested the equivalence principle with an unprecedented level of precision.

This is simply Galileo's experiment again now with higher precision. No surprise. So what is the meaning of this apparently ground breaking experiment? Well, it is presented as evidence that Einstein's General Theory of Relativity with a new explanation of gravitation, is correct. 

How can that be when the Equivalence Principle is a cornerstone of Newton's theory of gravitation? How can an experiment confirming Newton's theory be used to show that also General Relativity supposed to be different from Newton's theory, is correct? How can the same evidence be used to support both a basic theory like Newton's and a generalisation thereof like Einstein's supposed to be different? 

Experimentally evidence that Einstein's theory is better than Newton's, would require an experiment which agrees with Einstein's theory but not Newton's. An experiment confirming Newton's theory cannot serve this purpose. Yet the objective of the MICROSCOPE Satellite Experiment is just this! As an example of what modern physicists in the spirit of Einstein do today to advance physics.