Under the DOD Civilian Acq WF PDP, for phase I, do NH IVs count, since the rules say use the highest grade level, which is a GS-15 equivalent. I would assume all of NH-IVs fall into Phase IV?

The phases are designed/driven by general schedule grades, with GS14s (and their BB equivalents – not the entire broadband) effective October 2015. GS15s (and their BB equivalents) are mandated in Phase IV (Oct 2018). SRPE Policy, dated 10 July 2015, Paragraph 4a1-4.