Yes, SAP procurements using Part 13 are exempt from using the UCF, based on the list of exemptions at FAR 15.204.  However, you do not have to use the UCF.  

Per FAR 13.003  Policy.

Paragraph (g)(1) states that 

Authorized individuals shall make purchases in the simplified manner that is most suitable, efficient, and economical based on the circumstances of each acquisition. For acquisitions not expected to exceed The simplified acquisition threshold when acquiring other than commercial products or commercial services, use any appropriate combination of the procedures in parts  13, 14, 15, 35, or 36, including the use of Standard Form1442, Solicitation, Offer, and Award (Construction, Alteration, or Repair), for construction contracts.