In a nutshell, the story of NUMMI involves American GM workers building Toyota-designed/GM-branded vehicles using Toyota's radically different manufacturing processes. The plant itself was a smashing success for GM; the plant achieved much higher quality and productivity than any of GMs traditional plants, and it gave GM valuable insight into their rival's manufacturing and design processes.
But this insight into Toyota's processes failed to transform GM because the GM corporate culture was so entrenched. It took the company the better part of 20 years to really adopt these changes they learned in 1984, as they continued to bleed market share to the Japanese.
The point of that story is that I believe the corporate culture of any large tech company is equally entrenched, and in my experience it's this corporate culture that utterly determines how a company's products are designed and produced.
So it really doesn't matter how Apple does things, it only matters that they're different and successful; their competitors will be completely unable to react or change. Every company is full of powerful employees who have worked their entire careers to get where they are, and they will fight tooth and nail to prevent losing their position over anything else. Do you think all those PMs at Microsoft are going anywhere?
So companies like Microsoft, Motorola, HP, Acer, Nokia, Sony, and Nintendo can only do what they've always done. And if you look at their products, that's exactly what they continue to do in the face of a radically changing landscape. That's why a Toyota or an Apple or a Google is so truly threatening to their entrenched competitors. They achieve dramatically better results by doing things differently.