From all frames of reference an object thrown by an observer reach the same destination inexorably. The object launched accumulates the inertia of the mobile.
In the image above the object thrown by the observer on the plane will fall inexorably in his hands regardless of the shape of the trajectory is observed.
RELATIVE MOTION
In the video the ball will fall inexorably in the cart, althought we see that its trajectory was a straight line or a curve.
The shape of the trajectory (rectilinear, circular or parabolic) is an issue that does not interest to the Philochrony. Therefore, the Theory of Inexorability doesn't considere the reference frame of the observer.
The Theory of Inexorability unifies all reference frames.