I just can't stop coming back to the fact that even if the RAN takes every shortcut available to them, buying boats off-the-shelf from the US or UK and having Australian crews trained abroad, maybe even home-basing the boats in the US or UK, it's going to be decades before they could possibly operate a nuclear submarine competently.
If they want to build the boats in-country, and possibly even train their crews in Australia... I fully foresee them failing, no doubt after decades of trying having spent many tens of billions. Some future government will recognise the folly of a country of just 25 million trying to afford and acquire nuclear boats, and chop the project.
(For clarity: it's really, really hard to safely operate a nuclear submarine safely. Get it wrong and the results are catastrophic. To not get it wrong requires knowledge and experience I just can't see Australia being able to acquire and maintain with any level of independence.)
I imagine the French contact was to build boats capable of littoral surveillance, just without nuclear propulsion. I guess Australia thinks it can spend a bit more and get nuclear boats. Can't fault their ambition. They're going to get a hard reality check at some point.