Banking apps are not “websites” by coincidence they happen to be apps using same technology to show the interface but there is huge difference between website and web app.

This distinction is important especially because people are notoriously confusing the two and expect web apps to be like websites and conversely implement websites with tech that is supposed to be used to build web applications bloating internet pipes with JS where HTML and CSS would be sufficient.

There is a big difference, one is spelt “website” and the other “web app”.

Beyond that, the distinction is purely arbitrary. Same tech stacks, same delivery methods, and the same client-side display tools.