Entering Australia without a visa or Australian passport

Can an Australian citizen who holds the passport of another country enter Australia without a visa or Australian passport? From a bit of cursory Googling, it's not immediately clear... 

On an official Australian government website it says:

Australian passport holders do not need a visa to enter Australia. New Zealand passport holders can travel to Australia without a visa and obtain a visa on arrival at the airport.All other passport holders need the right visa to come to Australia.

They also say:

A passport is the best way to show that you are an Australian citizen. You might still be able to enter Australia if you are an Australian citizen without an Australian passport, but it will be more difficult. The airline might also stop you from boarding a plane to Australia.

Expanding on this, on another site, they say:

Take your Australian passport and use it to depart from and return to Australia. An Australian citizen cannot be granted a visa for Australia. When entering Australia, all Australians, including those who hold dual nationality, must be able to prove that they are an Australian citizen. An Australian passport is conclusive evidence of a person’s identity and citizenship and provides the holder with right of entry to Australia. An Australian citizen who arrives without an Australian passport may be delayed until their identity and claims to enter Australia have been checked. If a foreign passport holder claims to be an Australian citizen, immigration officers must confirm and verify this through official databases, which will cause delays. International airlines have an obligation to ensure that they only carry appropriately documented passengers to Australia. In the absence of an Australian passport, airlines are unable to verify a claim of Australian citizenship at the time of check-in and may refuse boarding. The airline may have to make inquiries with the Department of Immigration and Citizenship in Australia seeking approval to carry the passenger, which takes time and may cause delays.

A recent holiday in Australia from the UK, where my party included a dual UK / Australian citizen with only a UK passport, allowed my to test these statements. We took an Australian citizenship certificate to minimise delays, and were briefly held up at:

• Qantas check-in, before leaving the UK
• Australian immigration, after arriving in Australia
• Australian passport control, before leaving Australia

Each delay was roughly fifteen minutes, whilst a mysterious phone call was made. At no point were we made to feel that what we were doing was wrong, just unusual. In fact, an official from Australian immigration emphasised this.

If we were doing this regularly, we'd get an Australian passport to smooth the travel process, but for the occasional trip, this worked perfectly well.