When every piece is photographed and measured at each step, a defect stops being a mystery. You can see exactly where in the process a garment went out of spec: it was in spec at cutting, measurements were as expected after sewing. But at one factory, it's too small after the wash. Caught while it can still be fixed.
The same record adds up to a digital product passport: dated photos and measurements for every unit, from first cut to the shipping box.