where are you seeing the notifications ? I installed the update and just clicked "use location only while using app" for everything
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.
I have some apps, i.e. Unifi Protect, that requires access to background location to send activity alerts when nobody is home, and i frequently get alerts that this app has used my location in the background, and despite selecting "allow always" it will pop up again in a couple of weeks.
To further add insult to injury, i appear to have "trained" my wife so well that she defaults to selecting "deny" for apps she doesn't use, and "only when in use" to everything else, which then results in a flurry of motion alerts :)
This might hurt for example Tile. I think their “network effect” is somewhat depending on this kind of background location tracking.