They are actually being geographically and historically correct. Your perception of them being incorrect is actually influenced by the northern hemisphere bias of mapmakers. In reality, going northwards is no less “down” than going southwards is.
In the days before cars when most country people would have to travel long distances, they would do so by train.
The train depot was considered by the rail management as the home point, and every train would come “down” to them. In the Australian context, this is reinforced by all capitals being on the coast, so they would be nearly at sea level, so most up-country starting points would be at a higher altitude, so of course the trains would be coming down.