How do you know Mifune is showing IS watching him in an old movie
It has to be felt.
Actually in a couple of those clips he does some throws in a very distinctive fashion. Minimal movement, total connection, and he takes a much larger fella off instantaneously. Having been thrown that way via brute force and having been on the receiving end of someone doing it with tremendous grace and elegance using something other than the brute force, it is unmistakable. Okay, can't be 100% sure. Nor can I be 100% sure there is no such thing as unicorns. However, as you said, it has to be felt. And once you've felt it enough times in enough contexts you start to see more and more of the tell tale signs.
So yeah, the guy has some serious skills. Seems obvious from the video.