I do recall that in the past, Apple has been caught by unexpected large demand at a new product release, and their customers got disgruntled about it. Ramping production UP is harder and takes more time than cutting it DOWN. Finding component sources and assembly facilities takes months; slowing build rates can be done in days.
So perhaps -- perhaps -- Apple decided to get ahead of the bulge and have production high enough that they could, for once, cut back and relax rather than have to scramble and hustle with hair on fire. One wouldn't want to lose the opportunity to deliver product to a China-size market if it's there. If it doesn't materialize, one can back off with relatively little pain (by comparison).
But of course, that slowdown action is interpreted as The Sky Is Falling by those who make money when Apple sneezes.
Who knows what's really going down... not I.
I expect there's just as many people betting in the other direction, and motivated to spin the interpretations in the other direction, but the reports on the outlook for the Chinese economy appeared to be pretty gloomy from all quarters.
It remains to be seen if they just miscalculated the demand curve, or if the expected demand just isn't going to materialize at all.