Speed freak
Your understanding is exactly right. RNP values have absolutely nothing to do with any conventional navaid based procedures. Although we use managed nav to fly non-precision approaches, the primary reference is still the navaid itself which must be tuned, identified and displayed. In the case of an ILS you are actively tracking the radio beam itself.
Think of it this way, if an RNP were required how is it that a steam aircraft that has no RNAV capability whatsoever is able to fly the approach? In the case of the Airbus, both FMGC's could completely fail and you are still perfectly able (and legal) to fly any conventional navaid based procedure.
Whoever interviewed you does not know their stuff as well as you do.