I have seen those test results. The thing you have to remember is that it was not just about muzzleloading projectiles. One of their conclusions was that you don't get the same kind of fragmentation with the lower velocities of shotguns and muzzleloaders as you get with the centerfire rifles. (Unless of course if you use magnum loads on light powerbelts like you MD)
The whole thing started the year before last when some peta member in ND found lead in the venison that was donated to the food shelf. Then Minnesota ended up disposing of all the vension that had been donated here, even though no one has ever even gotten sick from ingesting lead in meat. Then they did this test firing different projectiles out of different types of guns into sheep.
In no way does it prove or disprove the well known fact that powerbelts fragment when overpowered.