Question about stitching mystery on CWU36

[anthonyhie]

I noticed that some cwu36 didn't have the same arm attachment. Some do not have double stitching. Some have simple stitching. Is there a particular reason?
Can the cwu jacket be custom ordered in the military context?

Here is a photo of the subject :

Others examples :

Thanks for your answers !

 

[Skyhawk]

Contractors usually have a little leeway to do certain parts how they want as long as it meets the specs. This results in some variance. Sizes specified and are supposed to adhere to the specs. There is usually an allowable tolerance of .5" to 1" in measurements.

 

[Skyhawk]

Here's the specs: