The top search response is for the Australian Parliament House's Parliamentary Paper No 63 -
Commonwealth Executive Power and Accountability Following Williams (No 2) (where Williams (No 2) is
Williams v Commonwealth (No. 2) (2014) 252 CLR 416, as opposed to
Williams v Commonwealth (2012) 248 CLR 156 (Williams (No. 1)).
Apart from the problem that "nationhood power" is essentially a legal construct that sits outside of the Constitution, there's prior High Court precedent, specifically Williams (Nos 1 and 2), that has found that the concept of a "nationhood power" does not trump the the division of legislative responsibilities spelled out in S.51. In the cases where the High Court has found that the "nationhood power" provides a legitimate basis for the Commonwealth exercising a power not otherwise articulated it has been largely related to S.61 - for example,
Davis v Commonwealth (1988) 166 CLR 97 regards the Commonwealth's power to establish the Australian Bicentennial Authority.
Then there's the matter of what exactly is "nationhood power"? The High Court has found that it is an implied executive power derived, in part, from Australia’s national status. And the only reason that the concept of "nationhood power" gets a run is that when the Constitution Act was passed in 1901, there were certain external national powers that Australia could not at that time exercise. For example, at the time Australia could not declare war or enter treaties. It was only after the retreat of the Crown through things like the Imperial Conferences of 1926 and 1930, the passage of the Statute of Westminster and the corresponding Australian legislation, the Statute of Westminster (Adoption) Act, and finally the Australia Acts, that Australia had the opportunity to fully exercise external powers.
With regards to what exactly falls under "nationhood power", the High Court routinely relies on a definition provided by Justice Mason in
Victoria v Commonwealth and Hayden (the AAP Case) (1975) 134 CLR 338; specifically he describd it as ‘a capacity to engage in enterprises and activities peculiarly adapted to the government of a nation and which cannot otherwise be carried on for the benefit of the nation'. It's often referred to as 'peculiarly adapted' test although the 'which cannot otherwise be carried on' element is also important.
On the basis that a determination on how best to manage health matters had been made at the outset of federation, there's an argument that the 'peculiarly adapted' test was done and dusted 120 years ago - the determination was that the Commonwealth was not 'peculiarly adapted' to manage the nation's health, that would be an activity that would be 'otherwise be carried on for the benefit of the nation' by the states. The fact that that arrangement was tested by a pandemic less than two decades later could be seen as an argument in its favour.
Further, without having to invoke "nationhood power" to support a Federal power grab, there are a range of mechanisms to provide for a nationally coordinated and effective response to national health emergencies, things like the Australian Health Ministers’ Advisory Council, the Australian Health Protection Principal Committee, the Advisory Committee on Vaccines and the like.
That'd be a matter for the High Court - just in case, you would probably want a summer hearing on the matter.