Why should he?
Plenty of things make a difference to the performance of a hi-fi system. All that James is doing (along with his conies such as myself) is warning people not to be taken in by some of the foolishness that unfortunately bloats the audio sites these days.
Usually these crackpot ideas carry a not so small price tag for the potential user, so all the more reason to be vocal in opposition.
I can do a multitude of small things to my room and system to change the performance. Move listening position by just a few inches (measurable), alter the speaker positioning by just a few degrees (measurable), alter the room furnishings (very measurable), swap out my competent SS amp for a valve one with several ohms output impedance (very measurable), use ultra-thin solid core speaker wire (measurable), change the TT mat, the bias on my tape machine ..... etc, etc.
All of that and a whole lot more will change your system, is often free of charge and is worthy of discussion.
But freezing bits of polycarbonate?
Christ, a domestic freezer doesn't even 'freeze' it for starters!
<hint - it ain't water>
Then we have the cables were, oddly enough, the claimed performance hike goes up in direct proportion to the degree by which you line the sellers pockets. Odd that