When I lock the screen while using any encrypted app (for eg MX player) and if I unlock the lock screen using fingerprint the app doesn't ask again for fingerprint but if I keep the app in background or remove it and again unlock the lock screen with fingerprint it ask for password as you can see in video👇🏻
My suggestion is it must ask for password even the screen is unlock with fingerprint whether the app is running in foreground as the screen was lock so it's necessary for privacy.
It only happens while using fingerprint as if I enter pattern lock then it ask for fingerprint please see it as it's a bug or not...IDK?