I'd say it's a little bit like automatic stabilisation. If everything in your frame moves in the same direction at the same speed, then it's probably the camera

I'd say it's a little bit like automatic stabilisation. If everything in your frame moves in the same direction at the same speed, then it's probably the camera moving, so you correct for it and the video becomes stable. Similarly you could see multiple things in the frame accelerating and decelerating at the same time and deduce it's not the things, but the camera that's doing that. That's the retiming part. Filling in frames is probably a whole lot more magic though..