Why would the rules have to change? It already accomodates a 2nd entry to NA for SA travel -- which would be the required rule change to allow JL47/48. The fact that it can use 1 sector instead of 2 is irrelevant for purposes of the rules (most of the UK-Australia flights are single flight number despite the stop). They might add the clarification that NA counts as a continent even if you just transit there, but that isn't an essential rule (it is implicit in the definition of continents).