The Australian threat analysis may be faulty
Australia seems to be perceiving a threat to its territorial integrity but without any major strategic threat to itself from any of the neighbours.
Does Australia have any unsolvable threat such as territorial claims from any of its neighbours or regional countries? There are no evidence of any such dispute.
Yes, there are a few issues relating to trade, mostly initiated by Australia. Consequently, China had blocked import some of Australian agricultural products.
Australia for some unknown reasons has entered the US-China competition in the Solomon Islands and the other Pacific islands. Australia siding with US would have obviously angered China & probably the perceived threat.
Australia has no strategic threat to its territorial integrity subject to the country maintaining safe distance between the two rivals.
The threat in the SCS does not concern Australia. Why get involved?