When I was a sacker in highschool and the grocery store got self-checkout booths, the staffing did not change. We still had 2 human lanes open during work week

When I was a sacker in highschool and the grocery store got self-checkout booths, the staffing did not change. We still had 2 human lanes open during work week hours but now with +4 self-checkout booths. So of course that's going to increase throughput. Also, not to mention all the times the few human lanes are clogged by people with 200 items that are holding up all the people just trying to buy a bag of cat food. Now my hometown grocery store has 8 self-checkout booths managed by a single person. Since those 8 self-checkout booths did not replace 8 human lanes, I'm not sure how you can argue that it did not increase throughput.