In ios 11 we now have "Add photos only" permission setting.

But how we now determinate which photo library access level is set?
[PHPhotoLibrary authorizationStatus] works only for "Read and Write" permission check. If app asked only for "Add photos only" permission then it stays PHAuthorizationStatusNotDetermined. If user changed it from "Read and Write" to "Add photos only" it gives PHAuthorizationStatusDenied.
So, how can I tell if my app have permissions to do "Export to Camera Roll" feature, which dosen't require read permissions?