Tour easiest recourse may be the ACCC https://www.accc.gov.au/consumers/co...r-damages-loss
Normally these are for physical products sold in Australia but do cover services, not aware of any USA DOT equivalent for Oz in terms of baggage compensation enforcement. You correctly state that there is statute, but I'll bet that the airlines engineered an exemption for their CofC's back in 1959. Still Australia has strict consumer law, and QF is an ethical airline, I've been treated very fairly by QF in past dealings when there were problems (but it wasnt adversarial and I spend a lot of money with QF, millions over the years). The airlines have found that people overstate the value of lost items in lost baggage by several hundred percent (by auditing the bags that eventually get found after being paid out), hence the pushback in the industry against the lost claims. Personally I've almost never had any of the restricted items in checked baggage in the past 20 years, more because I don't want to lose it than the $ value.