This is such a bad idea on so many levels it defies all logic to even see someone offer it for sale. One would be so much better off taking the money people would have to spend for the kit and the supplies and buying .22 ammunition with it, even at gouger prices. One would also be much better off using some sort of black powder muzzle loading rifle or cap and ball revolver instead of this abomination.
On the other hand, it does make a limited amount of sense to reload some of the obsolete rimfire cartridges such as the .56 Spencer or .44 Henry - assuming you had some fired cases to reload. But who has those?
Many, many years ago, I did some reloading of .30-30 cartridges using black powder and reloaded fired primers using toy cap gun caps. Remove the primer, remove the anvil, flatten the primer cup using a punch and hammer to pound out the firing pin indent, cutting the powder out of a cap using scissors, pushing it into the primer cup, replacing the anvil, and re-seating the primer into the case primer pocket. I had quite a few fired .30 Carbine bullets I used as projectiles. It actually did work, but I wouldn't bother today. It was far more work than the results justified.