You’re still misinterpreting the eligibility requirements, and it’s important because there are people who forget to take out insurance before they leave and may only remember, for example, as they arrive. Telling them they can’t get cover is potentially detrimental to them.
The requirements you have quoted above do not say ‘must have purchased before leaving australia’.
As i have said, there are several - ‘non-specialist’ policies - which happily provide cover after you have left Australia.
I bought one after a last minute trip to the USA and I’d forgotten to take out a policy before departure. No worries, signed up while I was there. Aussie company, same residency requirements you listed. There was a short waiting period to make sure you aren’t trying to claim for something that’s already happened.