While in the app switcher on android (I do not use iOS so I could not tell you if it happens where or not) you are able to see all your personal information.
It should be hidden, that is the point of me having a fingerprint on the app, so people can not just read my information. The RBS app does this and I think it is a great idea.
Monzo app right now:
Additionally the RBS app does not allow screenshots in the app. It may be controversial for some but I think monzo should also disable screenshots in the app in case of an accidentally screenshot or something, or at least implement a feature that covers personal information when taking a screenshot.