I remember when those were being sold in Shotgun News, but don't know anything of their history. The South African connection is even new to me.
The British shot at Communist insurgents in Malaysia in the 1950s with regular A5s. They had a special load for the purpose, buckshot with the nooks and crannies filled in with smaller shot. I guess the idea being that even a No 6 puncture might fester in the jungle and put a Red out of action.