All good mate, I mostly just try and stop the spread of misinformation on Aus gun laws. Most people don't know much about them.
The leaver actions are fast. The main difference is that you can leave your finger on the trigger for a pump and are meant to take it off for the leaver action, though you could do it with your non trigger hand. People are also buying left handed bolt action shotguns to get around this, though it's more awkward. All our shotguns have a capacity limit, usually 5 or less. It looks like these guys modified their barrel mags to hold more.
You're not wrong about wasted ammo, reliability and reload speed, but you have to think about the worst case scenarios. Situation: close range, large dense crowd, shooter with an unreasonable amount of ammunition, and best luck in the world with no jams or reliability issues. That's the formula for mass casualties. This is what our laws are effective at protecting against, primarily by limiting the rate of fire.
Haha. We have plenty of moron politicians. But typically all our legislation is usually written by public servants with expert advice and lawyers, and even they get it wrong sometimes. The politicians direct what they want, but most of them have never written a law. I assumed it worked this way in most places.