Airservices is technically correct on two grounds.
First, the only 'mandatory' provision in ICAO is the one obliging Australia to notify differences. Secondly, ICAO Annex 15 Chapter 4 (which details the content and format of AIP) only 'requires' a TOC. There is no mention of a separate index.
I'm surprised people are still paying for and using the paper version of AIP. It's masochistic.
As to the rest, here's an idea: Let's merge CASA and Airservices into a thing called the Department of Civil Aviation, reporting to a Minister for Aviation ....