Army Regulation 700-127 (https://armypubs.army.mil/epubs/DR_pubs/DR_a/pdf/web/ARN7460_R700_127_FINAL.pdf), Para 4–4. states “PSMs are required for all ACAT I, II, and III programs.”  Additionally, Army policy also requires that:

• “Prior to MS B, PEOs will assign a MATDEV PSM for each ACAT Program prior to, but no later than, program initiation. The PSM is a direct report to the MATDEV, PSM performance will be rated by the MATDEV (this responsibility will not be delegated).” (Para 4-4b.)
• “The PSM will be a key leadership position for ACAT I programs, and a critical acquisition position for ACAT II and III programs.” (Para 4-4d.)
• “Program Executive Officers are responsible for… assigning PSMs to all programs in their portfolios.” (Para 1-16)
• “Materiel Developers will… In coordination with the PEO, assign a PSM for each ACAT Program at program initiation.” (Para 1-18.c)
• “MATDEVs will assign a PSM to Joint programs.” (Para 4-9)

Seer also DA PAM 700-127 at https://armypubs.army.mil/epubs/DR_pubs/DR_a/pdf/web/DAPam%20700-127_Web_FINAL.pdf  for additional details.