The two sentences are addressing 2 different issues, and prob creating confusion.
Since most parts for DIY PC are manufactured in China (USB I/O cable, Power Button, Inlet Power Cable, PCIe Riser, Rubber Grommets, Screws and etc...). The ease of getting access to these parts in China makes it hard to justify making cases outside China. Especially if the volume is small, the extra cost for shipping and import tariff for said components is not worth it.
China has better shipping options than Taiwan, where the M1 is made. If the M1 was in China, we can ship to customers at a lower ccst and faster speed. Unfortunately, China and Taiwan really don't like each other, so there is a tariff to transport goods between them. The tariff is expensive enough to void advantages of shipping items made in Taiwan to China.