The Kiwis had one (or two) conversions APPEAR to be unsafe back in the late 1990s. The range authorities (not the NZNRA) made loud noises and banned all No.4 conversions, for what appear to be quite similar excuses. It was all the rage on the old fullbore list. No proof of actual danger, just the appearance of risk. The issue was pressed back upon the authorities who reacted with typical bristlance (a made up word for bristling with resistance) and repeated the ban in the face of all suggestion to the contrary.
The Canadians it must be noted, haven't bothered to care who shoots what for at least 20 yrs.