Does the MDA have the authority to waive the APB or would you have to go to the DAE?
IAW DODI 5000.02T https://www.esd.whs.mil/Portals/54/Documents/DD/issuances/dodi/500002T.PDF?ver=2020-01-23-144112-220
As a designated Acquisition Category (ACAT) III, the Component Acquisition Executive (CAE) or the individual designated by the CAE as the decision authority will review potential ACAT III materiel solutions. Table 3 lists the material that is statutory and regulatory required at each of the milestones and other life cycle decision points during the acquisition process. In consultation with the appropriate stakeholders, program managers may propose for MDA approval, tailoring of Regulatory program information. MDAs will document all information tailoring decisions. When there is a logical relationship between required documents, e.g., the Acquisition Strategy and the Life-Cycle Sustainment Plan, and consequent coordination can be streamlined, the MDA may approve combining these requirements.
Regarding the APB, per enclosure 1 table 3, it is "STATUTORY for MDAPs at Milestones B and C and the FRP decision; a Regulatory requirement at all other Program Type/Event combinations, including the required draft at Development RFP Release. For the APB, the draft due at RFP Release does not require CAE approval. For most programs the APB is not approved by the MDA until Milestone B, however. However if more information is required please see section 4 in DoDI 5000.02T for requirements at other than the identified decision points."
Again per enclosure 1 table 3 listed in the notes section - Moving right across a row, a checkmark (check) indicates the requirement for updated information in the APB. So for the ACAT III program being a regulatory requirement for the APB there should have been information update at MS-C, FRPDR, & Other.
So, the answer is an ACAT III program has a regulatory APB requirement and should be submitted and update IAW the DoDI5000.02T. Regulatory requirements can be waived. Your Program Manager is responsible for developing the APB. Since the APB is a summary of the program cost, schedule, and performance baselines, and is the fundamental binding agreement between the MDA, the CAE (if applicable), the PEO, and the Program Manager. The APB serves as the basis for reporting to the MDA through the DoD management information system. If it was waived, please see your program documentation that would have been sent to the ACAT III MDA IAW DoDI 5000.02T enclosure 1 table. The APB was required by regulation as indicated under “Life-Cycle Events” Dev RFP Rel for the first submission . Note if this is a program where CCA, a statutory requirement, is applicable (please see CCA compliance is detailed in section 3 of Enclosure 11) the APB should have been one of the documents submitted by your program.
There may be an argument for not including the APB unless it's necessary for the effective management of the program. Referring to the DOD 5000.01, 4.1.b.(1)
" “Tailor in” the regulatory information requirements that will be used to describe the management of the program. In this context, “tailoring-in” means that the PM will identify, and recommend for MDA/DA approval, the regulatory information that will be employed to document program plans and how that information will be formatted and provided for review by the decision authority. The PM’s recommendation will be reviewed by the MDA/DA, and the MDA/DA’s decision will be documented in an acquisition decision memorandum. MDAs/DAs will coordinate, when necessary, with other regulatory document approval authorities to facilitate implementation of this approach. Statutory requirements will not be waived unless a statute permits."
As you note, 5000.02T note that the APB is regulatory for non-ACAT 1 programs. Given that is close to completion, I think an argument could be made that an APB should not be tailored in at this point. The PM would make this recommendation to the MDA/DA who, if that person agrees, document their decision in the ADM.