Interesting article Honeyeater.
As a Kiwi and a manuka honey producer, my main issue with Aussies calling their honey manuka, is that in NZ we only have one species of leptospermum, but in Australia you have (from memory), 27 species.
Because of that, what Australia is selling as manuka honey, can taste very different from the honey that NZ sells, and has spent many years and many millions of dollars on research, development, and establishing the brand. What Australia is selling is a different honey, and in my view is damaging the manuka brand.
Also, here in NZ any manuka honey sold internationally has to be laboratory analysed to verify it's purity, but there are no standards at all in Australia, so Australian beekeepers can call any honey they like Manuka and send it overseas, this may also end up damaging the brand, and might account for the wide variation in tastes.
My own view is that Australia produces some very good honeys, but they should go back to calling them whatever they called them, before NZ established our Manuka honey as a high end product. Australia might do better for the beekeeping industry as a whole, to do their own research and development and marketing of their own unique honeys, and market their high end products under Australian names rather than a Maori name, and could broaden the world wide perception of honey in general, which would be good for us all.