Very curious. One flap indicates they are o.k. and the other does not. Unless of course RC are only using standard and superior proof similar to what is happening in Britain. That would mean that they are not suitable for Standard Proof; which is obvious, and the only proof above that it Superior Proof. The warning is there to stop their use in Standard proof guns and after that there is no alternative between the two.
Maybe RC could clarify. I've not bought any 3" magnum stuff for a long time so have no recent boxes to see if it is the same with British ones. As Larry says, if in doubt don't use them until RC clarify. Lagopus.....