That surprised me, too, because a previous version of the system used smaller bin stacks and no steps. Amazon could have gone in the other direction. The layou

That surprised me, too, because a previous version of the system used smaller bin stacks and no steps. Amazon could have gone in the other direction. The layout could be designed so that the picker sits on a swivel stool and never stands at all. That's what they do when they test robot picking - there's one human-sized robot arm on a turntable mount doing the picking. Humans would get fat with that layout.