In this case, it would be reasonable that the person who uses the app would be responsible. The app takes the image and labels every pearl with a number. So the person just needs to check there were no missing or mislabeled pearls, which is much easier than counting.
In the example I would expect the app to get it right every time. In a more fuzzy setting it would still be faster (thousands of times) and [generally] more accurate but a person can account for how important accuracy is.
I guess the numbering added to the image is brilliant. A human can gaze over that and see something wrong right away.