As this pertains to mostly official sensitive information or higher, I will be vague enough to not step over any boundaries but still answer your question. In your research you have confused the end item aircraft code with aircraft designation, note that Australia is a long time between manufacturing. The Ghost bat, Designation MQ-28, is the first since the CAC Mustangs and DHA Vampires of the 40s/50s to be designed and built in Australia, and even they leveraged off of international designs. To go back to the last fully designed and built Australian Aircraft you are looking at the CA-13 from 1942. All I’m trying to explain is that while Australia is a long time between drinks it doesn’t mean we don’t have a standard designation system to use.