There's a great deal of PRIVATE information on the various BDM certificates for each of the different states and territories that form the Federation of the Commonwealth of Australia. For example, my own birth certificate contains detailed information about each of my parents, each of my older siblings, the employer's details for each of my parents, the full names of my both my parents, including former names, full street addresses, names and qualifications of the medico and staff assisting, and a great deal more. Same amount of depth for each and every one of my NSW born ancestors who were born AFTER March 1856. Most of the Australian states and territories have similar depth of info.
This (long standing restricted access policy) means that from a family history perspective, we do not conduct our family history research in the same way that someone researching 20th century families in say England would research.
As an aside, may I mention that the quote that KGarrad has highlighted, comes from a current thread, and he is quoting from my post on that thread, although he has not yet acknowledged my post

on that thread
Compared with, for example, Australia?
Quoting from another thread:
May I gently mention that Civil registration for births, deaths and marriages are the responsibilities of each of the states and territories that make up the Federation of the Commonwealth of Australia. And in Australia, the information on BDMs is PRIVATE information, and therefore access to the non historic BDM registrations by members of the general public is restricted. (Unlike say quite recent English BDMs which seem to be readily available to members of the general public)
Our OP notes that George and his three children migrated to Queensland in the 1930s, where he re-married and had a further child. So may I note that in Queensland the BDM restrictions are 100 years for births, 30 years for deaths, 75 years for marriages.
https://www.qld.gov.au/law/births-deaths-marriages-and-divorces/family-history-research/information-and-how-to-access-and-order-records/information-you-can-access/
http://www.justice.qld.gov.au/__data/assets/pdf_file/0003/58341/Certificate-Access-Policy.pdf
http://www.rootschat.com/forum/index.php?topic=690010.0Cheers, JM (NSW centric)
ADD, These restricted access limitations are not unique to the eight jurisdictions that make up Australia .... New Zealand also has restricted access, and I understand that many of the states in the US of A do too.