What happens when a rod is pushed through the bore and the brush or patch holder or jag clears the muzzle. The rod via gravity will be pulled towards the center of the earth. During this process the rod will be stopped by the muzzle. Whatever that rod is made of it will grind dirt into the bore. If you use a vice and the rod contacts the muzzle on the same spot every time it clears the muzzle, the repetition of overcleaning in this manner will probably cause more damage than a bore snake would.
I have used a boresnake for so long and so much as a civilian and at war, that no amount of this or that theory will change the mind of those that know.