It all makes sense, they are required to know me for AML reasons, so the account creation step collects this data.
The bank is mobile first, so the account is activated through the app when my card arrives. Why would I have a username and password for the app that is used to create the account in first place? The app can keep it for me without exposing it to me ever. I can’t be phished for something that I don’t know and it is one less password to remember or take care.