It is the RNP capability and GLS that matter
Reference NAV, ...it is the RNP and GLS "CAPABILITY" that matters...
Note: not all RNP .1 is even equal. To actually fly real RNP based procedures (like the ones referenced),... The NG and Max are superior to any current european or south american offering, ...and the NG/Max are even equal to or superior to any other north american offering for actual path performance and capability. Yes, it is true that secondary features like some aspects of tuning could be updated, but that doesn't affect its excellent performance.
Reference IAN, ... IAN was never designed to address flying RF legs. That's why you simply use RNP capability with LNAV and VNAV for all those kinds of key beneficial procedures. IAN was originally invented simply to provide a better way to use the AP and various (e.g., EGPWS) protections, and use common flight deck procedures and annunciations, ...with a more sensible (straight-in) lateral and vertical path, typically when needing to fly classic straight-in based SIAP approaches.