The trouble with rifle companies is, they can make any kind of claims as to what their product can and can't do. When I tried to purchase the PA Pellet Flintlcock rifle (the company tried to change out the rifle for what they had in stock and increase the price. I wouldn't agree to it.) I did a lot of research in this rifle. And from all the people that shot it, they told me ...
yes it will shoot pellets but you need to duplex black powder behind the pellets for more consistent ignition.
yes it shoots other powders but you need to duplex black powder behind the main charge for more consistent ignition.
it shot best with pure good old black powder. Then there was no ignition problems other then a dull flint.
Personally to me a flintlock means black powder. Then there is little problem with reasons the rifle will not fire.