[kalleboo]

On iOS, photo write and read access are granted separately, so you can allow an app to only save photos.

Apps can also import photos without any permissions at all by invoking the system photo picker (where the user manually has to pick the photos one by one).

[Tsiklon]

Is it the case that when the app uses the system photo picker, that the app is only ever presented with the photos the user selects? In other words, the app doesn't have direct read access to the main photo library.

[londons_explore]

Correct.

This is true on both android and iOS, but on android the 'system' photo picker is an intent which fires up the gallery/google photos and typically has a pretty bad user experience, so not many app developers use it.