There is also a Grey area, at least as far as I have been able to read. If doing what some boutique blenders do, buying tobacco from duly licensed primary processors, mixing them together, heating, stoving, pressing, etc., perhaps with added ingredients for flavoring that are themselves FDA approved as, say, food additives, can be viewed as manufacturing under the law as it has been (very selectively) enforced by the BATFE, is it manufacturing as the FDA sees it under the (different) statute that they will be enforcing? That is a long winded question. But I have tried to find an answer and I can’t.
At least one primary processor has already pulled some of their previously available blending tobaccos from their catalog because they say it isn’t capable of being grandfathered and they don’t sell enough to file the paperwork that would qualify it otherwise. So, the inference to me is that their remaining offerings to the trade are ok to use. So does a shop mixing some 1Q with RLP 6 and calling it Geezers Dream require them to first file for FDA premarket approval? If they heat it up before they sell it, are they required to file ? If they put it in a noodle press? Spray it with Rosewater?
TL:DR. There are lots of outstanding questions. Some are probably best left unasked for now.