Its not what they could legally do, its the image they can conjure in the minds of the undeducated jury. While the argument applies to any handloads, upside down hollow base wadcutters could be easily demonised in the opinion of the non shooting public.
"Regular ammo wasn't deadly enough for him! No! ...etc."
More of a civil liability worry than a criminal one.
I love my reloads, and if thats what I had in the gun at home, I wouldn't be concerned, but, I don't take them out on the street.