That's interesting but in my state using a muzzle loader during the firearms season is not an option. They are separate and distinct seasons. State land firearms is actually a shotgun only affair.
Before the popularity of rifled shotgun barrels, state land shotgun season was largely a smooth bore season which utilized a more primitive type of barrel than the rifled muzzle loading barrel.
Even today, hunting with a single shot smooth bore shotgun has a more limited range than most muzzle loaders.
I don't use a smooth bore shotgun for hunting deer anymore but shotgun hunting is a great form of hunting. It's much like shooting a muzzle loading conical bullet, especially when using a 20 gauge.
A .20 gauge saboted lead slug starts out at about .40 caliber before it expands on impact.
Why this state keeps the seasons distinct is mostly for game management reasons. The shotgunners get 2nd crack at the deer which is during the main rut and after the long bow season. Then the muzzle loaders hunt last when their longer range guns aren't impeded as much by the foliage, the deer are more wary and the woods aren't as crowded.
Centerfire rifle hunting in this state is only allowed on private land, and now pistol hunting is an option here on private land for the first time.