There's a lot more that goes into shipping a product at this scale than just "having enough stock" you don't want to sit on millions and millions of assembled units and not get the return on the investment so you build up as much inventory as you can and then you release it and fill orders as necessary.
They could release to less countries and therefore have less demand for the new phones, but by purposefully releasing the phone to a larger audience and driving up the demand they can help fuel the "we must buy now or we're going to have to wait till November" crowd and on Monday or Tuesday of next week have a press release announcing yet again that Apple has sold a record number of units in their launch weekend.
Apple is the master at convincing people that the time to buy is now.![]()
Exactly ... example: Surface RT