The aberration angle would be incurred at the top of the medium envelope rather than on the ground, but the angle of the aberration would remain the same, medium or no medium. The velocity differential exists, and the existence of a medium will not wishfully make it go away. This provides experimental verification of the refutation. Things do not fall in 4-d. Things do not even move in 4-d.
All motion becomes geometrical, since time is an axis.
Describing gravity in 4-d, therefore, can only be done in terms of an appropriate curvature. But just like a chart of population growth does not contain any information about the reasons of population variations, a curved spacetime is not the reason for gravity. But the curve in the population chart can just be the fact of the population boom, communicated using a picture instead of numbers. The population chart cannot be the reason for the population boom. Similarly, a curved spacetime is only the fact of gravity, as told in a different language.