All five seem to be operating on the assumption that Apple cut its orders because the company is selling fewer iPhone 5s than expected — a theory undercut somewhat by the only two things Apple has said about iPhone 5 sales: That they broke records in September, when the device was first released, and last weekend, when it launched in China.

So are there other reasons Apple may have cut back on iPhone 5 parts orders? We’ve heard two competing theories:

• Apple is making the iPhone 5 more efficiently. As Business Insider‘s Jay Yarow put it: “Apple may have put in a bigger manufacturing order under the assumption that the iPhone 5 was going to be hard to make. Turns out it’s not that hard to make, so Apple can cut its order.”
• Apple is clearing the decks for a new iPhone in the June quarter. This is the theory favored by former Apple CEO John Sculley. “I think they’re going through a very significant change now in terms of product cycles,” he told CNBC. “Traditionally Apple introduces products once a year; now it’s really introducing products twice a year. The complexity of that from a supply chain is immense, and Apple seems to be doing it well. So, I think that people are underestimating just how well Apple is run, and just how successful the company can be when it gets to that twice-a-year product introduction cycle.”

In support of Sculley’s theory, Asymco‘s Horace Dediu has collected half a dozen pieces of what he describes as circumstantial evidence. They seem pretty convincing to me. See Does S stand for Spring?