I think your assumption that good physics == not fake does not hold for certain classes of faking, i.e. simulating the collision first and modifying the ball positions (or creating one or both balls wholesale) to match.
I mention this not to cast any doubt on the kicking video, but because there are a lot of good simulation tools nowadays and faking something up by working out the physics first is only going to get easier.
Well, if fakers make the effort to do the math (and physics), more power to them. It just makes this kind of video forensics a more interesting challenge. :)
I mention this not to cast any doubt on the kicking video, but because there are a lot of good simulation tools nowadays and faking something up by working out the physics first is only going to get easier.