Again, the only time that scenario works is if the dealer had already had a car on order for their stock, about to be built, and they assigned it to you and switched options to customize it for you. If the dealer has NO unsold stocks already ordered, it goes in on their next ordering opportunity, based on their allocations, and that COULD be many months before they even have a slot, and then it has to be built.
I was lucky, once I decided what I wanted, my dealer found one in the region another dealership was willing to trade, and I had it in my hands in about a week. If he had not been able to find one like that, they had one scheduled to be built for their stock that could have been modified to meet my desires, and it could have been built in a couple of weeks. BMW allows the dealers to modify an existing order almost up until the day it is supposed to start production with no penalty, and unless there's a shortage of the material for that option set, it will just get built as you asked rather than as the dealer originally ordered it (an example seems to be the Terra and the leather - that seems to be somewhat in short supply and slowing down orders for that option).
IOW, you might have to wait a fairly long time before the dealer gets another allocation and ordering opportunity, and a production number can't be assigned until that happens (at least as I understand things). When corporate sees that a dealer has a firm order for a vehicle, that can sometimes bump it up some in the cycle, but it is still based on allocations and available build slots.