Well again, I don't think it would help. You were not required to isolate at the address on your ID. For some there were probably very good reasons why they wouldn't (like family at home that they don't want to infect, or perhaps they are a renter sharing an apartment, or perhaps they have a nice holiday home they want to spend some time in, or maybe they don't even live in Australia? who knows).
That said, they know who the people are so I don't see handing them a nice big fine to be a big long term problem. I just truly hope they follow through with the threat.