Departures from Australia are subject to the Passenger Movement Charge,
https://www.homeaffairs.gov.au/trav/...nt-charge-(PMC)
Exemptions are specified in the legislation and include "transit passengers", which are defined as:
transit passenger means a person who arrives in Australia from a place outside Australia for the purpose only of a journey from that place to a place outside Australia and who departs from Australia: (a) in the case of a person who arrives in Australia on an aircraft and who departs from Australia on that aircraft or another aircraft: (i) without being immigration cleared within the meaning of section 172 of the Migration Act 1958; or (ii) if the person is so immigration cleared to enter Australia for reasons beyond the person’s control—as soon as it is reasonably practicable for the person to do so after those reasons no longer exist; or (b) in any other case:
(i) less than 48 hours after the person arrived in Australia; or (ii) if the person is prevented from departing from Australia less than 48 hours after the person arrived in Australia for reasons beyond the person’s control—as soon as it is reasonably practicable for the person to do so after those reasons no longer exist.
In essence, this means if you are immigration cleared to enter Australia, you are not a transit passenger. Whether an airline permits an overnight or <24 hour connection is superseded by the legislation in terms of calculating payment.