Whilst not providing a judgment either way, this is another example of the inconsistent application of a policy causing an issue when it's correctly applied.
Spot on.
What this shows is that either airline would have happily accepted an innocuously packed > 70% alcohol load of greater than 5L and been none the wiser, unless it was made so plainly obvious to them
and the check in agents knew what they were doing.
Should the worst have happened, I wonder whose heads would have been on the chopping block.
In short, the policy really lacks any power.
For whatever it was worth, I knew of these policies existing for a while - I remember reading the VA policy. I thought they were rather curious, and notwithstanding an overly cautious / risk adverse stance or the cynical money grubbing one, I can't think of other reasons for such restrictions. (Can't be duties as they don't exist between the states.)
It's moot for me as I've never seen the case (pun intended) to carry more than 5L of grog anyway, let alone 5L of alcohol-equivalent. It's nigh impossible on international trips due to duty free limits.
As for Qantas (or Virgin, or other carriers) being able to carry > 5L of alcohol on its aircraft, the only thing I can think of is that they have to have a lot of paperwork to support that. It could include risk assessments, manifests, DG related permits; I'm not sure if some of that is also tied to holding a liquor licence.