Your right and wrong, we have to wait until the main shipments start on monday, then until the resellers can ship them on which takes extra time. If the truly dont start main shipping from Apple until the 19th, theres no way Macmall and the like can get them on your doorstep before late the next week.
Another point is that resellers dont place orders like normal customers as you suggested, they have special contracts with their procurment departments to get a certain amount at a lower price (lets say a crate of 500) and this ensures their supply, but Apple have to make these first and logistically shipping 500 as one order is harder than 1 or even 50.
The last time the 17" came out about two years ago i remember this same thing happened exactly, Apple delayed the shipping by 2 weeks, and then i didnt get it until a further week after my delivery date and a lot of other people experienced the same thing. Although all other times ive ordered from Apple stuff has come well before the delivery date.