probably started by big brands so they can sell their names for more. The same guy also tested amps and pretty much everything anyone has believed about them, tubes etc, for decades is also bull. He used a few effect pedals and switches to make an amp that can mimic the famous brands he used as reference to a degree where I doubt anyone could tell the difference.

you can make an electric guitar and amp out of scraps and get whatever famous sound you want but a lot of people I have meet really don’t want to believe this after lining their walls with guitars with price tags I could never afford.