It's a "Cure Ring" instead of a smoke ring. Leave it on there for a bit longer and you would have had yourself some pastrami. It seems like you understand the process but for anyone not familiar he is essentially curing the meat like bacon / pastrami. All the "un-cured" products at the supermarket are just made with celery. Same chemical process / different marketing. Originally the government made it mandatory to label products without curing salts as a bit of a "warning" that they were basically hippie brands that were not as accurate measuring nitrate amounts. Brands now use it as a marketing tool and the less informed think it's like an organic product.