Even if they are getting by with it, I still wouldn't recommend doing it. The reason is even low pressure smokeless loads have a vastly different pressure curve than blackpowder. The smokeless don't explode but does burn and produce pressure (gases) extremely fast whereas blackpowder explodes but at a very slow rate of speed, thus producing less pressure overall.
If you want to get away from loading blackpowder I would suggest 1 of the blackpowder substitutes suck as american pioneer powder, blackhorn 209, 777, or the like. They'll load with the exact same measured amount as blackpowder, still produce the smoke, but don't build up fouling and attract moisture like blackpowder and pyrodex will. Neil