I've been doing research, and although I have found blog pieces claiming what you are saying, they also say things like this:
"The Australian Classification Board (ACB) has confirmed to Somebody Think Of The Children that a person’s overall appearance is used by the Board to determine whether someone appears to look under the age of 18 in a film or publication.
…
Asked whether breast size was considered by the Board when determining age, McDonald said he had no further comment to make."
and also, according to wikipedia:
"Restrictions on the “X18+” category of videos were tightened[10] in 2000 including the restrictions on portrayal of fetishes, and of actors who appear to be minors, including women with a small bra cup size, after failed attempts by the Howard government to ban the category entirely, and then replace it with a new “NVE” category which would have had similar restrictions."
regarding the cartoons:
"In December 2008, a man from Sydney was convicted with possessing child pornography after sexually explicit pictures of children characters from The Simpsons were found on his computer. The NSW Supreme Court upheld[8] a Local Court decision that the animated Simpsons characters "depicted", and thus "could be considered", real people; however the conviction does not extend to other Australian states and was based on solely the pornography laws within NSW. Many have mistaken this as a Federal nation-wide ban which does not exist.[9] Controversy arose over the perceived ban on small breasted women in pornography after a South Australian court established that if a consenting adult in pornography were 'reasonably' deemed to look under the age of consent, then they could be considered depictions of child pornography. Criteria described stated "small breasts" as one of few examples, leading to the outrage. The classification law is again not Federal or nation-wide and regards only South Australia.[10]"
I had a look at some publicly available legal/governmental stuff, e.g. this briefing paper:
http://www.parliament.nsw.gov.au/prod/parlment/publications....
Interestingly, from the statistics at the end, over half of the criminal cases in SA were for producing child porn (s. 63(a) Produce child pornography), but exactly two thirds of the convictions were for possessing child porn (s. 63A(1)(a) Possess child pornography).
Possession was four times more likely to result in imprisonment than production. Possession was 3 times more likely to result in a suspended sentence than production.
I'm absolutely amazed by this. Basically the cops caught a bunch of people producing kiddie porn, and then the courts let them go, whereas possession of porn means you get the book thrown at you. Honestly I would have thought it was the other way around.
It seems (from the briefing) that the legal justification for this slant is that producing child porn harms 1 child, whereas to possess a large collection of child porn is to participate in the harm of thousands of children.
This legal doctrine is particularly interesting (and hard to justify) in the case of cartoons/manga, because there is no actual child being harmed in those cases (though there is justifiable concern about actual movies of real abuses being 'cartoonised' in order to get around restrictions).
In summary:
The actual laws around this are much murkier than I originally thought. Much is left up to the discretion of the censors on a case by case basis, there have been previous attempts to ban small cup sizes (as far back as 2000 or possibly even earlier), there has been a trend towards larger cup sizes in australian porn because of pressure applied by the censors, and the censors refuse to rule out anything to do with cup size. States have different rules than Federal, and in many cases (as in the simpsons character debacle) what happens in a State court may be mis-attributed as being the rule at the Federal level.
Moreover, if you are accussed of possessing kiddie porn in Australia they will throw the fucking book at you (so don't do it (!!!!)). Whereas actually producing kiddie porn in Australia earns you nothing more than a slap with a wet bus ticket in most cases.
I find your accusations and subsequent downvoting rude and baseless. You may not like the sex party, but they are one of the few organisations in Australian politics devoted to transparency in government (for their particular hot-button issue anyway).
Given that there are documented attempts by the Australian government to ban small cup sizes in porn dating back over a decade, I find their accusations much more plausible than your own.