I have a feeling that this "test" was intentionally cherry picked to show what they wanted to show.
Most "audiophile" people have perfect equipment setups, or at least close-enough ones. When you design a test like this you're really only testing the ability of the medium to conduct electricity. You're not actually measuring anything if it conducts electricity at all. Four of the Nine correctly guessed which one was actually the wire, and none of them guessed correctly any of the other materials.
Which begs the question, what was the resistance of each material? Because the only thing that should have happened if it was on the analog end of the circuit, was the audio volume being reduced. There shouldn't have been any noise introduced because in order for noise to be introduced there has to be a RF source being directed at the wire. Wire is a conductor, hence it acts as a radio antenna. But a Banana is not. Same with wet mud.
The "audiophile" monster cables, everyone knew was a BS product claim. Any "audio" analog cable was as good as the next one as long as the resistance was was under a certain amount. Raw speaker wire and a RCA stereo cable is exactly the same wire, just with a connector on the end. This "test" is basically the other way around, where the electrical signal was just forced through another medium.
At any rate, I don't feel this test proved anything except that the signal loss wasn't high enough to notice.