Paywalled, but even the bit I could read I don't agree with. It works great where I live, and totally does cut down on lines! The supermarkets I go to usually have one manned line, and 6-8 self-checkout terminals manned by a single employee. In one discount store the person manning the normal line also has the self-checkout, unless someone else is nearby, and that isn't ideal. But even then, I get to stroll past people who can't figure the system out, and maniacs who are either paying with coins or arguing over lettuce prices.
It works fine 80-90% of the time, and the employees are pretty swift to help, because it's usually one of two problems: Either I'm buying alcohol, or fruit and veg that's in season doesn't have uniform weight. Otherwise it works great.
The one grocery store I regularly visit that doesn't have it is a nuisance, because I wait in line every time.