Limited stock doesn't matter when it comes to preorders. Video game consoles have very limited stock for months after launch and they still do preorders and everyone I've gotten I've just went to the store hours after opening on launch day and picked up my preorder with no lines.
But isn't it the stores selling the consoles that are doing preorders and not the company itself? I know not all stores have done preorders for the newest consoles. So isn't that argument a little different?
When Apple does preorders, you're ordering through Apple and its being sent to your address. And I believe the only product they've ever done reserve it in store was the iPad 1. So it's not something they do all the time.
The stores have to have stock to sell.