This article fails to recognize the difference between throughput and latency. A single queue optimizes for latency, since slow customers don't stall the ones behind them. If cashiers work faster in a multiple queue setup, then this configuration will optimize for throughput while still losing at latency.

As a customer, all you care about is latency: How long you spend waiting in line. As a store owner, you also care about throughput: How many cashiers you need to process some number of customers per unit time. A store owner that cares about customer satisfaction will still care about latency, of course.