This was Steve Jobs' original vision for the iPhone, before he relented and launched the App Store. Maybe it was the correct one.

Not exactly. The iPhone launched with no App Store at all. No exceptions for financial institutions. I allow financial institution apps on my phone because I believe that the security guarantees on iOS are stronger than on my desktop OS, and also that the customer relationship with the banks/etc are more valuable (to the bank) when their apps are not infected with tracking and ads, etc. And of course, the bank knows a lot about me anyway due to transaction history, and they're well-regulated, understand privacy, etc.

Also, I have trouble believing that the App Store and public SDKs went from "not on the roadmap" to "released" in one year. I know it's the popular narrative, but I feel like there must be more to the story. It's plausible that they were being worked on but a final management decision hadn't been made to launch them?