Priority codes are used in two different ways. The codes above 10 are used by your dealer to signal to ford the order in which that dealer would prefer their ordered vehicles to be built. Your dealer sets this number and it only matters if that dealer has multiple orders for same/similar vehicles.
Priority codes below ten are controlled by Ford and set the priority they wish to reflect. This can occur at any time after the order is in place for different reasons. If scheduling is adjusting codes and they move to one or two, that's getting close, if they go up, there's a concern of some sort.
If the regional representative for your dealer is "helping out" they can move the priority to below ten. If Ford wants a hot model out in public, one again. Replacing a manufacture screwup, one again.
Why it doesn't matter. Your dealer might only have one or two vehicles in that same model/style. Then it doesn't matter. Your dealer has, let's say 100, and sets the code based on who ordered first. Then it's fair and it doesn't matter.
Ford pulled my 2021 W2X for scheduling two days after it was ordered, in Nov 2020 when the ordering opened. Made it priority one, locked out any changes for months, issued a vin# in January, stayed locked for building and was built it in July. Priority one for 8 months.
It's become all about body code and parts available.