Ok. I’ve had a chat with tech at RAAus, and here’s my understanding of the situation (no guarantees that I’ve got it 100% correct 🫣).
Approval to fly over closely settled areas is a CASA issue. RAAus has no jurisdiction in this area. There is an RAAus employee who, putting his private hat on, is a CASA Approved Person (AP) and can issue the required document. In fact, any AP can issue it, though many charge significant amounts to do so (because, as I think Nev & Turbo noted, they take the legal liability for doing so).
Many classes of RAAus aircraft are automatically covered; LSA, legacy, etc. However, amateur built after the introduction of XYZ piece of legislation (I think 10 and 19 rego) are not, and require the aforementioned approval. As you can imagine, no one is hovering over Sydney’s northern VFR lane, inspecting approval documents as you fly past, but if you do have to do an unintended glide approach to some park, road (or roof!) and you don’t have CASA approval, then your insurers may have something to say about it… 😳