Names are a matter of state jurisdiction.
All the Passport Office can do is reflect, and work with,
the requirements of the states' registers.
That's useless because the Op has not decided if that is what he wants to do. I posted that link to the passport office because it has a good list of different name changing scenarios. If he did decide to change his name then yes, he will need the Australian RBDM Registry as mentioned many times in the link.