I'm inclined to think if OpenAI notified them, something happened. The other possibility is that this is marketing, look how scary our model is, must be good. Weird it happened in June and is only now being reported.

One thing that tweaked my interest is that in the first report from the ABC they say

It is understood an AI crawler, which is an automated program that scans websites and collects information from them, was able to find a security workaround to access the data.

Later reports regarding the medicare server hack report that files were changed on the server to enable access, a breach, so it didn't just walk its way in.

I think it likely they tacked a red team (hacker) agent onto their web crawler to scrape up more data for training sets (super irresponsible, negligent and likely a felony). Perhaps they turned it loose on Australia considering us a soft target, perhaps they just turned it loose worldwide and no-one noticed much (unlikely) and they're testing the waters notifying us. Whatever the case, that's some cowboy shit, and there should be legal consequences.

ETA: Here is documentation of similar attacks on Canada and US around the same time.