This attributes the drop to a price increase, but I wonder if rising anti-western sentiment has hurt western brands in China generally. Yes I know iPhones are made in China, it's probably still perceived as a western brand relative to Huawei.
I suspect that the (perhaps unintentional) "message" is that this is another sign.
Big Apple campus in North Cal is where all components of iPhone success are made: hardware and software design, marketing, logistics and strategy planning.