All to do with RNP vs RNAV performanced based requirements.
NPA = RNP requirement (containment) for example, RNP0.3, or RNP 0.15(AR)
SID typically RNAV1
Comes down to definitions.
Required Navigation Performance (RNP) Specification. Area navigation specification that includes the performance control and alerting requirement, designated by the prefix RNP; e.g., RNP 4, RNP APCH, RNP AR APCH.
Area Navigation (RNAV) Specification.- Area navigation specification that does not include the performance control and alerting requirement, designated by the prefix RNAV; e.g., RNAV 5, RNAV 2, RNAV 1.
Also, depends on your certification standard:
5) If only TSO-C129 equipment is used to meet RNAV 1 and RNAV 2 requirements, it is necessary to confirm RAIM availability for the flight route (route and time) foreseen, using current GNSS satellite information.
6) If only TSO-C145/C146 equipment is used to meet RNAV requirements, the pilot/operator does not need to make any prediction if it is confirmed that the wide area augmentation system (WAAS) coverage is available along the entire flight route.
Taken from:
https://www.icao.int/SAM/eDocuments/...NAV2%20eng.pdf