It is in the specific case that you don't have biometric or PIN login set up on the device and you use a password manager that doesn't require authentication. In that case, the only factor is "something you have". Otherwise, it is still a multi-factor authentication because the device itself still represents "something you have", and your device unlock represents "something you know" or "something you are".
I would stop using bank requiring phone app to do banking, simple as that, both my main EU accounts use sms verification codes and extra password, which is fine with me. If they will require an app, they will lose customer.