Bryan needs to pretend that he knows nothing and speak with some top Benchrest or F class shooters, who are winning with tuners, and learn why they decided to use them (as Erik did) and how they set them up.
IMO if we limit ourselves to what we already understand, we will never discover anything completely new. Sometimes we need to just try things and see what happens. If it works we learned something. If it does not, we still learned something. The important thing to understand is that just because we do not understand why, does not mean it does or does not work.
My old friend Del Bishop once told me that when testing a load change, that I needed to make a change that was large enough to be seen, and that even that changing something made accuracy worse, he learned that it mattered.
I would say that Bryan may be under the impression that he knows how everything related to ballistics works, and he may, but strictly speaking, this is not that.
IMO changing the position of a weight on the muzzle of a barrel effects the point in the muzzles travel where the bullets that will form a group on the target are released within that cycle.
As far as test design goes, I think that he needs to work with a winning benchrest shooter, supplying barrel bullets and powder, and let the shooter demonstrate what he has seen in his own testing. Then he needs to use the same equipment and shooting technique to duplicate those results. At that point he will be a lot more qualified to comment on and test tuners.