Unless they've changed something, the only box of it I've had (44-40) was indeed loaded with black powder, at least it smelled, shot and fouled like real black powder. However, I did not taste the fouling to be certain.
I'd give Black Dawg Cartridge a call if concerned.
Barney Fife: "Nip it, nip it, nip it!"
Andy Griffith:"Oh now Barn'...."