They use assembly lines in China, but to say they don't manufacture anything is false. Every single part of the assembly line is under their control. Apple take into consideration manufacturing and other constraints during the course of product design. Also, while they might contract the "sourcing" of some pretty standard materials, Apple are renowned for their supply chain management, and have been known to switch to backup suppliers on a dime for whatever reason. Make no mistake, Apple are known for great hardware because.... they make great hardware a cut above the rest, and to say they're not responsible for their products is just...silly.