How does Quettra Portrait get the list of installed apps on non-jailbroken iOS devices?

According to the Quettra Portrait for iOS Privacy Policy they manage to get a list of installed apps on iOS. What's more, they're able to do this from an App Store approved app on non-jailbroken devices. Every Google/StackOverflow search I've done on the matter suggests that this is impossible, but Quettra is somehow able to do it without raising the ire of Apple. Any ideas?

via Chebli Mohamed