| http://australia.gov.au/about-australia/our-country/time

That web page is (obviously) aimed at foreigners. Australians don't
consult the web to find out what the time is ... When talking about
things for outsiders, it is natural to call things "Australian xxx"
(whether it is beaches, schools, or timezones). A web site aimed at
foreign tourists might very well give details about Australian beaches,
or Australian roads, or even Australian time - but inside Australia
you're very unlikely to consider that you're driving on this Australian
road to get to some Australian beach (at some Australian time).