I don't buy it. Gluing two huge thick pieces of plastic to the place on your guitar that is supposed to vibrate must have an affect of tone.
Tons of stuff has an effect on the tone of a guitar such as: what material is your pick made of, are you fingerpicking, do you play with your fingernails, what gauge and type of stings are on the guitar, scale length, nut and saddle material, is it a 12 or 14 fret guitar, how you attack the stings vs some other guitar player, is the guitar 60 years old or 2 years old, what wood is the guitar made from, does your guitar have a rounded plastic back, and certainly are there two huge pieces of plastic glued to the top.
You guy discuss this stuff here to ad nauseam, yet refuse to believe two massive guards have any effect on tone. Seriously.