I've recently received a couple of packages for goods I ordered (and paid for) back in May. Having received refunds I now have to re-pay. I'm convinced that there is a big pile of "held" parcels sitting in an AusPost warehouse somewhere, and every now and then an employee goes to the pile and picks a package at random and puts it back in the active system so it gets delivered.
It's a management decision. AusPost gets eyeballed for cuts every year when the Big G is looking for some spare money, so the PostMaster developed a "Hostage" policy.
Every now and then they send out an ear, or a finger....