I originally had written premiers and PM's offices, not sure why I edited it. It wasn't a statement about federalism but about where power was located
within each level of government.
Obviously the judiciary is much less powerful here than the US, but my point was how power has been stripped away from party members, legislatures, the civil service, and most of the political executive. Even senior ministers have effectively no political power whatsoever, they're just sent out with their lines to read. All the power is concentrated within the PMO (or Number 10 in UK parlance), which nowadays solely dictates party strategy and policy.
As for the WA border closure, if you read the judgement it did not say that the constitution only applies to the trade of goods. In Australia constitutional rights can simply be overridden by necessity. You saw the same with the implied right to political communication which has been routinely ignored, as in the Bolt case. If you want to read up on this, look up the doctrine of structured proportionality especially as it's been applied since McCloy. Basically governments can flagrantly breach the constitution and then it's up to the courts to decide whether the transgression was justified based off their own value-judgements. The court was satisfied there was a public health justification for the closure, so s92 goes into the bin.
Realistically until Kiefel and Keane retire, Australians don't have any genuine constitutional rights because they'll just extend the doctrine of structured proportionality to whatever constitutional right is in question. "Non-absolute" rights are simply not rights in any sense of the word.