According to reports from Nikkei, Apple would have started to buy NAND for iPhone also from the Chinese Yangtze Memory Technologies.

According to initial information, Apple will use these NAND memory chips on the new iPhone and other devices that will be sold in China. Currently, most of the NAND memories used on the iPhone are produced by Toshiba, but now it seems that Apple wants to diversify the offer at least in the Chinese market.
It is likely that Apple's choice is political: to improve relations with the Chinese government, the Cupertino company would have decided to entrust the supply of these NAND memories to a local company, at least as regards the devices that will be sold in China