The Australian rock seems to be "natural;" it looks far too similar to dead coral branches to be aquacultured manmade rock and too irregular to be manmade branch rock. The sustainability aspect probably comes from the the rocks growing from and then separating off reefs during storms, which is how most "natural" live rock is formed (but this means the sustainability of the rock depends on how fast the coral, that forms the rock, grows, which is probably why "natural" live rock is not usually considered sustainable).
The majority of the patches look like Coralline.
Walt Smith Rock?