How does this reduce the number of parts on a car? Like, okay, you currently build a vehicle by dragging a hulk down a moving line. This says leave the hulk i

How does this reduce the number of parts on a car? Like, okay, you currently build a vehicle by dragging a hulk down a moving line. This says leave the hulk in one place, and bring the parts to it. It on its face appears to be less efficient.