Experience.
My little amp, a Forte' 4a has better sound when I dampened the external heatsink fins. High frequency information was cleaner, more precise. I use chunks of rubber bottle stoppers cut into thinner strips, staggered across the fins. This was also mentioned in some article I read about MY AMP, later.
Yes, it is difficult to know if someone is just making stuff up, if they are an expert in the field, if they have actually experienced the phenomena, if they are just totally looney anyway, if they have studied it with an open mind, if they have studied it with extreme bias blinding them to anything but what they are certain has to be, because that is what makes sense to them....