Bullet construction has a lot to do with it, also the newer muzzleloader's are trying to make flatter shooting possible. The 45-70 with a 500 gr. gullet with 70 gr. of black powder is a real good killer of buffalo, deer and bear, but the trajectory is also a factor, even though shots with the 45-70 can be made out to 200 to 400 yards, again the trajectory is a big factor.
In my opinion it is not a bunch of hype, it is a fact that the new muzzleloader's with there 100 and 150 gr. powder charges are knocking on the rifle trajectory's and are more of 200 yards guns than 100 yard guns.
So in closing, there is more to it than your observation.