Normally, myCloud can only upload photos as long as the app is open and a few minutes after the app is closed. This was designed by Apple to terminate unnecessary processes that may still be running in the background.
If you activate the option "Upload in the background", the app is also able to upload data. This is done by checking whether the location has changed. This check makes it possible to ensure that the upload continues in the background, since the app remains' active' in the background.
For this reason, the myCloud app asks for permission to access the location data of your iPhone/iPad. This allows you to upload photos even if the app is not open when you automatically back up.
It is important to know that your location data will neither be evaluated for this function nor passed on to third parties. Since only significant site changes are requested, enabling this setting does not lead to increased power consumption.
Automatic saving also works if you do not activate the option "Upload in the background". However, for the reasons mentioned earlier, it is necessary to open the app regularly so that the photos are uploaded.