This is on the FAQ page https://docs.microsoft.com/en-us/azure/active-directory/user-help/user-help-auth-app-faq
Q. What is App Lock, and how can I use it to help to keep me more secure?
A: App Lock helps keep your one-time verification codes, app information, and app settings more secure. When App Lock is enabled, you’ll be asked to authenticate using your device PIN or biometric every time you open Authenticator. App Lock
also helps ensure that you’re the only one who can approve notifications by prompting for your PIN or biometric any time you approve a sign-in notification. You can turn App Lock on or off on the Authenticator Settings page. By default, App Lock is turned
on when you set up a PIN or biometric on your device. Unfortunately, there's no guarantee that App Lock will stop someone from accessing Authenticator. That's because device registration can happen in other locations
outside of Authenticator, such as in Android account settings or in the Company Portal app.
My question is, what does the underscored,highlighted sentence mean? thanks.