It will take me some time to find where I read it but in two seperate occassions well respected (old time) designers made that comment. Simply due to amateurs being fearless to experiment. My comment would be their love and loyalty to the technology.
However, this notion refers specifically for the valve technology. Solid state would never tolerate that if one did not know exactly what he/she was doing. Hence latest advancements in this technology such as D-class amps carry the signatures of designers such as Bruno Putzeys.