Bloggs:
Aterpster, page 35 details the Airbus SOP for RNPs: AP off by Minimum minus 50ft. CC's interpretation is reasonable in this case, as Airbus obviously is treating an RNP as an NPA, even though it is technically a 3D approach. From my not-current Boeing 737 FCTM (never flew it), the AP and ATS are disconnected AT the DA on an RNP-AR (SAAAR) approach.
I work with RNP AR quite a bit, but I am not qualified to fly it, since I no longer fly. I don't know at what point various U.S. operators disconnect on an RNP AR. DA would seem reasonable. But, in the U.S. on all RNP AR approaches the DA-point is the MAP, just as with all approaches with a DA instead of a MDA. The fact that VNKT has the RNP AR MAP at the threshold makes no sense to me. Also, in the U.S., an RNP AR approach would be NOTAMed OTS by the FAA during a period where the threshold is displaced for construction. The FAA could issue a new RNP AR approach to account for the displaced threshold but they are not inclined to work nearly that fast.
The FAA does not consider RNP AR to be an NPA.