It's certainly not uncommon for Apple to preload Macs with different builds of OS X than what is on the DVD. It's possible the video may be more of a 'Welcome to The Mac' than 'Welcome to OS X' - in which case they'd likely make it play when someone first boots their new Mac, but for people upgrading from Snow Leopard it wouldn't be required.
That's what I just argued, but apparently I'm wrong...