Not something that subtle. Do you have any proof that it makes a difference? Have YOU heard the difference? We can go back and forth answering each question with another question, but that doesn't prove anything. We're not talking about the difference between a non-treated room to a treated room, or recording in a bedroom as opposed to a garage. Those things would make a difference. We're talking about putting piece of plywood under a singer, putting headphones on that singer, blasting a backing track through the headphones while the singer sings, and expecting that piece of wood to have an audible difference to what the singer hears in the headphones. Seriously.
Well! I have heard of goal post shifting but dragging new ones in? Were did "blasting backing tracks" come from? Might just be some gentle chords. What absent son would be doing.
And if you recall I mention some 75% of a room, about 106 sq feet of hardboard in my case. Not "a bit o wood under the singer"!
Dave.