They'll usually pop up unexpectedly and say something like "Data Leaking App has used your location while running in the background 3 times in the last 24 hours

They'll usually pop up unexpectedly and say something like "Data Leaking App has used your location while running in the background 3 times in the last 24 hours. Do you want to continue allowing this?" and it'll give me a prompt to disable location services for that app completely, allow while the app is in the background, while it's in focus, or allow always. Depending on what permissions the app actually needs, the prompt is slightly different each time. It's a new feature due to the more fine-grained permissions that are allowed now on iOS. It prevents apps that you may have previously allowed location access to (when it was just binary) from adding all these new "features" to use your location in ways that weren't disclosed that way initially.