Yes, whilst RNAV does not have to involve GPS, indeed the first RNAV routes were in the early 70s before any GPS satellites were launched, it only really worked once the system was available. Switching off the P code was Clinton’s gift to the world & allowed civ GPS to be accurate enough for precise navigation. The GA world in particular would be screwed by the P code being switched back on although I believe that more recent GPS satellites aren’t enabled with it.