Given I2's experience, another interesting question would be why does a Brinkmann smoker provide a defined ring, while using charcoal in a 'shack produces an overall pink color. A theory: the Cookshack operates at a lower temperature, thus allowing nitrate-laden smoke to penetrate all the way through before the meat becomes so warm that the smokering reaction stops. In the Brinkmann, the inside of the meat is already grey by the time the smoke has penetrated 3/8".
Another experiment which could be a final proof would be to treat a brisket with TQ as above, then slow-roast it on a rack in a regular oven. Even though it's not BBQ at all, it should have a smoke ring. Might be a waste of a brisket, altho it might be ok as pot roast.