You look enough like one that every bank in the universe hates you. Why? Because no goods or services are being exchanged in an easily-reversible way.
When a chargeback happens, it is the processing bank who must immediately make good. Not you the merchant. The bank.
As you can imagine, they really don't like that. And so different businesses are treated differently. If you buy and sell physical goods, you are less likely to have your account locked because there is the option for repair, return or replacement as part of the settlement. You are more likely to have physical assets that the bank could seize. A shopfront address where they can send process servers. Etc etc.
But a TPPA takes money in one hand and sends it with the other. The entire model is moving money to and fro. That means, when a chargeback hits the bank ... you might have stopped being to and become fro.
Unsurprisingly, TPPAs have an unusually rate of both chargeback (shady "subscription" schemes) and of there being insufficient deposited cash on hand when a chargeback arrives (ditto).
That you put in an anti-fraud system doesn't really matter to a bank. Anybody can say they did. What you get is a polite nod; they will still feed your business model and transactions data into their own anti-fraud system. If you score badly, expect to be frozen. Especially if you start moving transactions of a size that attract the interest of AUSTRAC.
Finally, the Commonwealth Bank is a retail or consumer bank. That's its history, it's baked right into their operational DNA. Both NAB and Westpac are generally considered to be better at business banking. I've no idea what ANZ's reputation is meant to be.
I suspect NAB got Pin because they're the only bank allowing you to deposit multiple currencies in a single account. Everyone else requires you to open separate accounts for separate currencies.
How do I know all this? The business model I'm working on is a TPPA. When I discuss it with banks, what they want is a locked reserve that they can get chargebacks from. The most generous I've been quoted is 30% of my cash locked for rolling 90 day increments.