The rep is just not aware that the 5500 is available with the integral fin; the 5500 is marketed as a replacement window but when I have some one that wants a higher quality new construction window I sell them the 5500 with the fin.
The 5050 does not have a integral fin option but the UV11 snap in fin can be applied to the exterior accessory grove. I don't like the snap in fin and would rather use the ProFinish Contractor in this case.
You can e-mail the rep the image below that shows that the integral fin can be selected for the 5500 in Simonton order entry system.
Click on the image to enlarge