Put another way, the "FMGS lateral and Vertical guidance" is non-precision. You can use it for published RNAV/RNP approaches, you can use it to program/simulate/overlay with other published non-precision approaches (VOR and NDB).
But you cannot (or should not) use it for published precision approaches (ILS, LOC, etc.) - not accurate enough (yet). Skip the RNAV/VNAV, fly the real radio guidance beams (NAV 1 radio).