From the story: "For instance, instead of sending product- and assembly-related information from China to Cupertino for a decision, engineers in China would also include their analysis. And China-based engineers who in the past generally would have reported problems to Cupertino would instead send proposals for resolving the problem, the people said."
There are no trade secrets being divulged or passed on to competitors with respect to iPhone assembly. It's simply granting Chinese technicians and assemblers the power to resolve assembly related issues as they come up when setting up an assembly line, or assembly issues discovered while in production. Instead of involving a US-based Apple engineer to resolve the issue.
As any iPhone competitor can simply purchase an iPhone on the open market and then take it apart to see how it is assembled, which commodity parts are used, etc., there's nothing to worry about. There's nothing secret about that
The detailed design, special signal processing, design tricks/efficiences etc., of iPhone embedded in custom chips which is proprietary is not revealed.
Sure, a photolithomicrograph of chip dies might reveal something interesting after a ton of analysis and work. But again, simply purchasing an iPhone from the Apple Store, Best Buy, and a hundred other places, disassembling the phone and removing and de-lidding the chips, would give a competitor making photolithomicrographs of chip die the same information.
