〈 Berger | Dillon 〉

Is it though? It's not free fall since air resistance is not negligible...

Well, yea.. experimental constraints

But that's the point. It's not Einstein's equivalence principle because they are likely falling at steady velocity (in contrast to free falling due to gravity)... so it's just galilean relativity.

Well the point is that you can certainly see that they are approximately weightless by the ball’s trajectory, which is Einstein’s equivalence principle.. The qualitative approximation seems justified to me

Sorry to disagree. If the drag is different for objects with different masses such that the terminal velocities are equal, which I think it's the case, then they fall at the same rate... and you see what you see. In this case equivalence principle just doesn't apply