Anyway at about 6:06 into the video Bob Carver discusses his friend that did the testing.
So a video of Bob Carver in the 1980's saying he heard from some guy .... :)
Credible claims tend to be reproduced, especially when they end up in selling bigger, more expensive equipment. On top of that, we have our own experience, and that of many other audiophiles here. If power were the limiting factor for accuracy I think we'd hear more of it.
Based on age, lack of detailed description of the experiment, and lack of corroboration of a very easy to duplicate claim this claim does not pass my smell test.
As with all things in science and engineering, I leave the door open to more research.
Best,
E