Some New iMacs Marked ‘Assembled in USA’
December 4th, 2012Via: Apple Insider:
Apple may be taking some of the burden of assembling the new iMac off Chinese supply partners by performing parts of assembly in the U.S., as a number of newly-purchased standard units are showing an “Assembled in USA” notation usually reserved for made-to-order machines.

This looks to me like a simple case of less demand for the made-to-order business. Rather than lay off the made-to-order staff (which have a higher training cost) they keep them busy assembling standard units. This also takes the pressure off their Chinese partners and gives them positive PR as a bonus.