Maybe because the Mac Pro doesn't require special parts to be made ahead of time in China. But I don't know about the first iPhone, nor did I follow rumors back then.
sure, but it's almost all bespoke but also made and assembled in the USA. Perhaps easier to control the leaks. And A lot of automated systems involved.
Reminds me of The NeXT Factory steve jobs made in the 80s.
http://www.youtube.com/watch?v=dSj6kvv7_Sg