Yeah, no thanks. I would not trust my money with a bank like that. A lot of fraud prevention is based on obscurity, and multiple steps of hurdles to make it easy to reverse a transaction. There's a reason money transfer takes a few days.
Source: I work in a tangential field
The reason a money transfer takes a few days is because ACH is based on SFTPing back and forth fixed-column ASCII text files.
In other countries there is not this delay.
That said, money transfers take a couple of days because most interbank clearing houses were modelled after paper-based batch processes where people shuffle through paper a few times a day.
There are several real-time payment schemes in the world. Retail customers in the UK mostly use Faster Payments (FPS) for interbank transfers and they clear within a few seconds.
For instance, reddit provides it's public source code but has all of its anti fraud stuff wrapped into a separate repo that is not public. This provides a lot of flexibility that wouldn't be available if it were all public. And sure, some of it is of temporary value ("we are catching this cheating teqnique specifically, until they realise that it's not working anymore") but the fraud arms race is much easier for the atackee if it is slowed down a bit by such temporary measures