To expand on that:
the performance aspect is always going to be very similar, since there's only really so many ways you can judge a performance.
However, an AMEB exam is pretty much all performance and no theory/general knowledge. VCE music, however, is at least 50% theory (I think? I did what used to be called music solo performance - in 2005 - so I have nfi what it's like now. Haha oh god I'm ancient).
Those who are great at AMEB exams might be so because they are extremely musical performers. Being good at the theory is a whole other issue though.
The exception is if you have done A.Mus or L.Mus, because those exams have significant general knowledge portions. Also obviously it's compulsory to have passed grade 5 and 6 theory respectively so generally, people who've done the diploma exams would have a good grounding in that respect too.
I say generally because there are always exceptions, e.g. although I have my LMus I got 1 point above the fail mark for grade 6 theory (BOOYAH) because I hated that shit and was terrible at it
But in general, there is not a lot of correlation between the two.