Just because the product is "in their custody," doesn't mean that their QC will necessarily adhere to the specifications of the company contracting the fabrication. Unless the company that hired them demands 100% inspection (all units), and has that written into their contract language, the contractor will only spot check a small percentage before sending them out the door. Lots of goods go through somebody's "custody," yet many times they arrive as non-conforming goods. That is true, whether the distance is 10,000 or 10 miles. I agree, every unit should be inspected. And modern QC methods employ checks along the entire mfg process, not just a final inspection. Crappy welds, bad parts, damage, etc., should be caught in-process before it's shipped to the company. Then, the company should perform its own inspection of each unit that arrives into their inventory, before shipping it to the customer.
My point is not about "where it's made." This isn't a U.S. vs. China dichotomy. It's about the level of control a company has over the processes employed by the contract manufacturer. There are methods of monitoring contract mfrs, like ISO-9000 standards, audits, etc., but those may be out of the reach of most smaller companies. Total Quality Management requires trained eyes to watch throughout the entire process.