ok465:
This one's interesting. You need an authorization to get to 3973 or 4079 on the RNP 'Zulu', but you can fly the LNAV/VNAV on the GPS 'Yankee' to 3952
Nobody said it would be easy.
It is tough. The pilot has to be able to read and analyze.
But, since few outside the airline world will ever be able to qualify for RNP AR, it becomes somewhat closer to easy.
Seriously, RNP AR is a great option for the aviation elite where difficult terrain would otherwise prevent a straight-in IAP. But, the airlines have driven the gross overuse of RNP AR where the only benefits are supposed fuel savings.