I am in same boat on one of my 3 preorders. On my 10/1-10/6 delivery for my wife's 6+ they only charged the AppleCare portion so far. On the orders delivering on 9/19 they charged the full amount. So I think Apple may wait to know she your and mine ships before charging the card.
Not true, it's charged when you order it, if you can't see it on your credit card statement then that's because of your bank processing time. It stops people from reserving iPhones with a fake card or a card that has $10 on it etc. Means that everyone who orders one on release day are real customers.