I've seen that before. I can't see why anyone would want to do that. Since the powder goes in the breech it's not legal for ML season, and ballistically it's not on par with most centerfires. Most of all, it makes it much easier to screw up and start pushing a bullet down the barrel after you already have powder (and more importantly PRIMER) in the breech.
Of course, from the manufacturer's perspective, you'll be buying your loads from them so it's great. No thanks, I don't even use pellets.