Checkpoint one: PBN is a mandatory part of the Type Rating chckride. For many years, even so it is not listed on the endorsement anymore as a unique skill and becomes embedded.
Then: How many training departments actively teach that for Baro-VNAV 3D approach (this case), the altitude distance checks are futile, not part of the system or certification, and better not be done in lieu of the important stuff? (sound of brains exploding..., sure). There are critical items to verify, about 4 and QNH being one of the 2 more severe - does not have self-monitoring and alerting.
That is why the Aircraft should automatically compare the QNH put (during cruise or early descent) into the FMGC approach page with the QNH set on the FCU during transition and give an alarm if off by more than one.
With the increase in PBN, we need more protection against wrong QNH. This would lead to a strong safety net against wrong QNH information or wrong setting.