Hi Peter. No, that would not be the reason. Priority codes of 10-19 (10 being best priority, 19 being lowest priority) are assigned by the Dealership for regular retail orders. It is completely up to the individual Dealership as to what code to assign. Commodity/parts shortages do not affect the Priority code, and vice-a-versa.
On the other hand, Priority codes of 1-9 are assigned by Ford Corporate. They usually are assigned for replacement orders for things like Lemon Law vehicles, buybacks, vehicles damaged in transit, customers whose last name begins with an "F" and ends with "ord", etc. etc. etc.
Once a Priority code is set and the vehicle is ordered/accepted, and your Dealership has allocation for that particular vehicle, that is when commodity/parts shortages will affect when the vehicle is scheduled and built. At that point, the better your Priority code is for that particular vehicle, as opposed to other orders from the same Dealership for the same vehicle model, the sooner yours will be scheduled/built.
It gets a bit more involved, but that is a simple explanation.
Keep us updated and good luck.