Read Hornady's disclaimer for the ammunition on the bottom of the link in Post #1.
I realize it may be more of a joke than anything else, but do you think that disclaimer could stand up in court, if someone used one of those "for zombies only" rounds in an otherwise "good" SD shooting (against a normal, living person...)?
Idk what (if anything) makes these rounds different, but I know there are some varmint bullets out there designed to "explode" on impact with prairie dog type animals. Maybe these zombie max rounds have something similar, which is why Hornady included the disclaimer?
Or maybe the rounds are garbage, and Hornady want to avoid liability in the event someone tries to use them as standard SD ammo, and ends up dead due to poor performance? This seems more likely to me.