Well I did take it slightly out of the context. But the concept is that. The US has more of a management role rather than a putting hard metal assets in there role.Poor wording or lost in translation IMO but trilateral cooperation to effectively keep tabs on Chinese boats doesn't seem like a bad idea, especially if they want to try create some kind of CASD posture.
We will definitely need 12 subs (or more) to have regular patrols of the SCS (and the Indian ocean).
But I think the question is still valid. What sort of navy does Australia need to "look after" the Indian, South China and Pacific ocean and Australia's interests in those three areas.