Uh, they do if it’s a rifle, and the first line says “a muzzle-loading rifle”. A smooth bore you would be right, but muzzle loading rifles sure do leave rifling marks.
no. There is a plastic sabot
A patched round ball does not have rifling marks - the marks are on the patch that drops off a short distance in front o the rifle.
A saboted round also does not have rifling marks - marks are on the sabot just like the patched round ball.
A slug round operates on the minnie ball principle and will have the rifling marks.