Is this happening because States Treasury want to hang on to the money as long as possible? Is this long process of payment due to that kind of setup? Don't you think we should insist that a public authority pays its debts in a timely manner, in general, as a matter of course, as a shining example to its people? I was brought up to pay my debts on time. Isn't this one area where the States could actually prove themselves as a caring Government that does not resort to these pretty, in my opinion, underhand, measures to keep the money in the Treasury pockets longer to gain the most interest.
You are happy and able to sort the matter out by your own due diligence but others are not in a position to do this unless they are in the know, or, know someone who can.
A small Sole Trader, for example, is not able to fight a big corporation or public body, they have no amunition. They would be shot down by the first officious employee at the reception desk. Having said that I do know of departments that have extremely polite and well mannered people operating their reception areas.