Low earth orbit isn't perfect either. You still have micro gravity. And the experiment requires a lot of power, and very sensitive instruments to measure the phenomenon. How do you get sensitive instruments which are expected to be operating near their error threshold into orbit without damaging them?
Orbital experiments will have to be smaller, and use less power, so the effects will even be smaller. But the instruments will have to be tough enough to withstand 5G. And the apparatus could still be introducing other errors, like coolant momentum, which also isn't magically eliminated by being in space.
