I think the best practice there is to "prime" the user before they see the iOS permission prompts. Something like "your phone will now ask for permission to access your location. We need this to do x,y,z.."
Sure, but my point is that for this very specific one (app may use location in the background) we are unable to do the priming as this one will be displayed by the app automatically (as opposed to most/all other such popups).