They probably excluded Curio and Relic licenses, who are not licensed to sell firearms as a source of income. A friend of mine bought a machine to put jackets on bullets. He says he has to get an FFL as an ammunition manufacturer to do this, even if he only intends to use the bullets for his own reloading. He also has a Dillon 550B, which he uses to crank out thousands of rounds for personal consumption. This does not require an FFL.
If this makes absolutely no sense to you, then you are beginning to understand the maze of firearms laws in this country.