I certainly agree with you that a Zener diode could be used in the typical Zener regulator circuit, but it would be slightly more helpful to point to his mistake. In his example Vin=5V, Vout=3.3V ...

Since the 1970s the voltage reference inside the highest precision commercial voltmeters has been a zener diode. For example, the current “champion”, the HP/Agilent3548A is based on an LTZ1000.