I pretty much disagree with that being a good solution.
Well, maybe it's not "good", but it IS the "best one among several less-than-perfect solutions", to accomplish the goals that are SHARED by you, me, AND law enforcement: (a) Ethical & humane hunting of the animals, (b) Allowing hunters to hunt hogs to reduce the number of hogs and encouraging the purchase of hunting licenses, and recover said hogs for consumption, and (c) effectively curb deer poaching the greatest extent reasonably practical.
That is, 'less you got a better one.
AT THIS TIME, I refuse to believe that (a) is not a goal for law enforcement (i.e. I refuse to believe that the state/law enforcement WANTS us to shoot them with BB shot, not recover them, and let them suffer and die a long horrible death simply to accomplish the end of reducing their numbers). Hopefully they won't ever prove me wrong on that.
The rule is absolute silliness when you think about it, though, because any hunter that is good enough to put a hog down with a rimfire to the CNS, is also gonna be good enough of a shot to put a deer down with a shot to the CNS, *IFF* they are so inclined to criminally poach a deer. So the rule doesn't in any way help with poaching, seems to me, since there's an end run by a determined poacher any way you slice it. You can't regulate a criminal bent on crime by regulating the type of gear used by people you WANT to be out there hunting hogs, anymore than you can stop robbers from using guns in robberies by regulating that law-abiding citizens cannot have standard-capacity handguns and semi-auto rifles with certain ergonomic-enhancement features. Stupid, stupid, stupid rule!!!