Actually Cady there's a lot that can be gleaned by just watching someone move. You have on more than one occasion referenced Sam Chin as good source material, so I looked him up on youtube and watched some of his clips. While what he's demonstrating isn't Aikido by any stretch, I can see that his power, stability, balance etc. are generated and maintained via a tight degree of mind/body coordination. That tells me that what we are discussing in the Internal Training in Aikido forum transcends any particular style.
Ron, things can be gleaned from video if the viewer is experienced in what is being shown, and knows what to look for. For most, all that's seen is the effect, with no indication of what the cause is.
A video clip of someone working the "6 directions" would look like someone just standing there. If a partner were to push on the stander.... on the chest, on the back, on either shoulder, on a hip... what the viewer would see is the stander not budging or showing any signs of imbalance. And if the stander were to return the pusher's energy to him, you would see a person standing still, but the pusher getting popped or bounced back.
It wouldn't be very instructive in terms of how things are happening, though certainly the effects would interest people or cause them to say "That's fake!"