Partially true, it is calibrated for some load, not all. they have different BDCs if I remember right. The rifle, muzzleloader and now shotgun.
Go to the Nikon website and pull off the data for the circle distances and use Exbal or any other program to do a drop chart for your exact load no matter what bullet you are using. You simply need the bullet weight, MV and BC.
Go to prbullets.com
and look at their double duplex bullets, loads and tricks for accurizing encores or other muzzleloaders.
Their 195 double duplex is the flattest muzzleloading bullet shot today and accurate.