While not speaking with real authority, I can repeat what I've been told by a couple retail suppliers. They admit that they are not fiber or yarn manufacturers. They are packagers. Some of them even disagree on material differences like Antron and Z-lon being the same. In a few cases there is an attitude of, "If I don't have it, you don't need it." This business is very competitive and they are trying to minimize their inventories while setting themselves up as having unique products.
The situation is even more complex when it comes to dubbing, with the added variable of dying different colors.
One resolution to this dilema is why some tyers like to stay with natural materials. There aren't many varieties of white calf body hair or gray squirrel tail.