JR: You are conflating the broadcast rules with the carriage of serviceable VHF rules.
If the circumstances of your flight require you to have a serviceable VHF, you have to comply with the broadcast rules.
If the circumstances of your flight do not require you to have a serviceable VHF but you nonetheless choose to fly with a VHF and it’s serviceable, you have to comply with the broadcast rules.
If the circumstances of your flight do not require you to have a serviceable VHF and you choose to fly without a VHF, or you choose to fly with a VHF that is not serviceable, you do not have to comply with the broadcast rules.
The question whether the circumstances of a flight require a serviceable VHF depends on, among other things, whether the flight will be in the vicinity of a registered or certified aerodrome.
Many places marked as aerodromes on aeronautical charts are not registered or certified aerodromes. Any other place not marked at all is, by definition, not registered or certified. Hence at those places it is very imprudent to assume everyone is listening to and broadcasting on VHF.
Simple.
The question to the VFR pilots and the instructor of VFR pilots in the Melbourne area - and the question at the heart of this thread - is not about whether someone has to have a serviceable VHF. It’s about the frequency they monitor and broadcast on, if they are required to have or choose to have a serviceable VHF.
Simple.