From PANS OPS -
1.4 USE OF FLIGHT MANAGEMENT SYSTEM (FMS)/ AREA NAVIGATION (RNAV) EQUIPMENT
1.4.1 Where FMS/RNAV equipment is available, it may be used to fly conventional procedures provided:
a) the procedure is monitored using the basic display normally associated with that procedure; and
b) the tolerances for flight using raw data on the basic display are complied with.
My take on this is - Tolerances of raw raw data can only be complied with if raw data is monitored ( as in a) and to monitor a Nav aid it has to be identified (aurally or auto if installed). Whether this actually happens day to day is another matter......