Based on my experience with gubmnt regulations here I submit the whole thing has nothing to do with killing power and will merely be enforced for the purpose of collecting fine money to fund the game department and also to provide an insurance escape for guides/professionals.

Here's how it works;

Daryl gets snagged packin a .17 on a leopard hunt. He gets fined R1000 and must sign a waiver that if the leopard makes kabobs out of his forearm his Pro is not subject to suit or game infraction.

Just my twee Rand!