I believe the Dangerous Goods License you are referring to is for the physical transport of dangerous goods - driver training. https://www.sa.gov.au/topics/business-and-trade/licensing/mining/transporting-dangerous-goods

It's not the same thing.  The Australia Post eParcel Contract and subsequent training refers to the packaging - how to bubble wrap perfume, etc. correctly so that it's safe for road transportation through the Australia Post network.