Time period has a lot to do with it.
The Ned Roberts classic, The Muzzle Loading Caplock Rifle, hardly mentions the use of round balls, dealing instead with a lot of various slug style projectiles. It even mentions using sealed ignition with modern rifle primers on heavy target rifles. However, for the most part, the shooting discussed, both hunting and target, is post Civil War. So, in the case of later style sidelock or underhammer percussion rifles, yeah, a lead or lead alloy conical bullet can be traditional. On a hunting or offhand target rifle, I still think "traditional" should be exposed ignition using a percussion cap
When it gets to flintlocks... well there might have been a flintlock or two that did not shoot round balls. But I have never heard of one.
The rifle pictured will never be mistaken for an original. However, it is probably as close as my first caplock, a birthday present in 1968, even if that gun had a wood stock and regular steel barrel.
Someone mentioned coil springs. I doubt if any pre-1870 (or later) had 'em. But, I'll bet there were not any cast "vee" mainsprings and frizzen springs either. That is what is on the vast majority of locks sold today.
If it is a sidelock with exposed ignition, iron sights, loose powder, (NOT pellets) and the projectile is lead or lead alloy patched with cloth or paper it is traditional. Some rifles like Civil War muskets or sporting rifles intended for conicals can skip the patching.
