Any insight into which of the two policy references would take precedence? Whether the FDO should be the HCA Designee/PEO or the SDO (recognizing that these two could be the same person, but not necessarily).
AFI 63-138 "implements the requirements and processes of the Federal Acquisition Regulation (FAR), Defense FAR Supplement (DFARS), AF FAR Supplement (AFFARS) and Department of Defense Instruction (DoDI) 5000.74, Defense Acquisition of Services." So in other words, the AFI is carrying out the requirements and processes of the AFFARS. Service acquisitions do have their own specific roles established in DoDI 5000.74 and AFI 63-138, therefore the AFI is implementing roles and responsibilities specific to services.
If there is confusion between those roles and others stated elsewhere, the applicable AF Contracting channels will need to provide the clarification of roles.