This is a story that went viral in 2010, and originated in a tendentious claim from Fiona Patten that Australian censors would target A-cup performers in porn, for fear of encouraging paedophilia (performers “who are or appear to be persons under the age of 18”).
The terse response from the Australian Classification Board was that they only made case-by-case decisions on classifying film and publications, although a “person’s overall appearance” was used to determine whether they looked underage.