One of the issues that we don't usually think of is that each assembly plant makes several different model cars. Edge and Flex crossover vehicles are built in Oakville, Ontario, Canada alongside related Lincoln models.
Each model is placed in the production line separately according to demand and when the that goal number of vehicles are made, the plant shuts down, re-tools/reschedules and begins making another model Ford or Lincoln.
If you are lucky enough to place an order just as the Flex assembly line is scheduled your ordered car will be built as soon as assembly is started, a quick order for you. If you have to wait while 25,000 Edge, 5,000 Lincolns and a few MKT's are built first it can take extra months before the Flex line will again be produced.
The actual time needed to assemble a vehicle is less than a week, the rest of the delivery time is because of parts scheduling and transportation.
There are other factors too, your build priority is given a number, the faster builds have a better priority number.
There are parts shortages for special orders too, these add to the delivery time.