It can in fact be MORE nitrate salts, because there's a minimum level needed to cure meats, and since celery salt or whatever celery-based product you're using

It can in fact be MORE nitrate salts, because there's a minimum level needed to cure meats, and since celery salt or whatever celery-based product you're using is less consistent in the amount of nitrate included, you have to use enough to guarantee that everything gets enough nitrate, which means that some of what you make will have substantially more nitrate than foods that aren't labelled 'nitrate free.'