They’re sufficiently represented because those bodies are resourced by companies and NGOs. Indigenous people don’t have those same resources, and simply allocating them through normal government process (as has happened in the past) can simply be undone by successive governments for political/ideological reasons.
Constitutional amendment prevents that from happening. It guarantees they always have a voice.
No real benefit, just changes the account you need to ensure has enough funds available. I had a similar setup previously, just used the redraw as the savings since you get a better interest rate.
I don’t know about other banks, but the CBA now lets you nominate multiple accounts as offsets, plus having a mortgage redraw account. That way, it doesn’t matter where your money is kept, it all counts towards reducing your interest. Makes a difference.