Requirements for a banking app (or even a retail app) is not like you might expect on a FANG-type app. Focus would be on functionality, stability, possibly ease of use (but way down the line), and security. I'm guessing management is not too bothered about app size and banking mgmt won't be overly technically focused.
Incidentally I was maintaining a cross platform mobile app for a major UK company. Between Android versions of the fairly ancient framework the app size grew 2 or 3 fold. There were a couple of issues, one was js minification was failing before it was wrapped into a native app by the framework, I think I fixed that in the build file. Also both the ARM and x86 libraries were being included in the APK even though we were only targeting one particular device series. Removing one of these almost halved the file size. It was only really the guy managing the devices and device builds that cared about this, the business wouldn't have noticed.
Incidentally I was maintaining a cross platform mobile app for a major UK company. Between Android versions of the fairly ancient framework the app size grew 2 or 3 fold. There were a couple of issues, one was js minification was failing before it was wrapped into a native app by the framework, I think I fixed that in the build file. Also both the ARM and x86 libraries were being included in the APK even though we were only targeting one particular device series. Removing one of these almost halved the file size. It was only really the guy managing the devices and device builds that cared about this, the business wouldn't have noticed.