RNP AR capability is only available in LNAV/VNAV which is a step back as all other approaches are flown in approach mode (IAN).
Excuse my ack of knowledge in this area. Why is RNAV/RNP with LNAV/VNAV a step back? What should it be?
I am unconvinced by IAN. Sort of like an ILS but isn't with different constraints, limitations and annunciations. Making something like but not quite and requiring extra knwledge and procedures is not KISS in my book, because you still need to proficient with VS and NVAV approaches too!