Hi John,
Very naughty to do that.
I agree.
Some crews seem to believe that the published Jeppesen / Aerad Non Precision Approach, (based on radio aids) can be replaced by the RNAV display for the overlay.
Building one's own approach in the FMC / FMGC with an undetected error will only mislead the crew. The overlay method was supposed to enhance situational awareness but some to seem to believe it can now be used in stead of the published approach.
If the Jep plate says RNAV GNSS / DME/DME then "fill your boots" - else you must display and monitor the published aids.