We had all our 737 classics without GPS certified to P-RNAV and could fly everything down to RNP 0,5 legally with them, except for pure GPS-Procedures.
If the SID is charted as RNAV(GNSS) then the ANSP has not assessed the DME/DME coverage and has only protected the procedure for GNSS (GPS). I would call that a pure GPS procedure. If the ANSP has done a DME/DME assessment then the chart title should just be RNAV - no '/GPS' - and then the RNP<0.5 would apply.