Don't be silly. I'm not suggesting that that they can know the exact number of phones to the person, but they've done enough launches that they can reasonably project demand. The fact that the phones started having ship times of "October" within hours of going on sales shows that they weren't even close to meeting the demand.
you should read guy kawasaki's "the apple way"
he explains one of the shifts of apple's production cycle to a "pull" vs. "push."
in push production a company, let's use sony, ms, or samsung (since they all use push) makes billions of units and then puts them out in front of the consumer at various price points and incentives, using billions of dollars of advertisement, and making sure that their retail partners are incentivized to push their product over the competitors through special pricing programs.
the company has to convince its target customer population that they want its products more than the competitions.
apple's pull tactic, however, uses strategic marketing to create demand among the user base. the user base shows up at the store already wanting the product. the demand is present before they walk in the door...before they even get in their car in the morning to drive to the store.
this tactic allows apple to stream line its production cycle and meet demand more closely as it dwindles down (versus at the outset when it's highest) and minimize stock space and discounted offerings for closeouts.
this was one of the revolutionary production tactics that Jobs is credited with when business majors credit him with having some level of genius. similar to how Henry Ford revolutionized automobile production. He didn't invent wheels or cars but he did change the landscape of how they were made and pioneered techniques that cut margins and raised profits.
this also enables apple to have all those flashy retail outlets without having to stock their shelves with product that no one will end up buying toward the end of a release cycle.
this isn't *just* some artificial method to manufacture demand. it's a legitimate and savvy way to manage retail stock in a fast paced consumer market where a smart and timely release like google's motoX can wipe out a less prepared competitor.