The old day VFR syllabus stated the candidate must be able to navigate using a 1:1,000,000 scale map (i.e a WAC). Those were not the exact words but I don't have an old syllabus handy.
The latest day VFR syllabus simply states:
- Selects and prepares appropriate visual navigation charts suitable for the intended flight
Obviously a VNC could be suitable. Most ATOs have the opinion that a CPL test candidate should be able to navigate using a WAC. All that I've spoken to are happy for the candidate to use a VNC for assistance, but the WAC is the primary tool used for navigation.
As discussed above, WACs cover all of Australian, VNCs don't. How many fresh charter pilots are going to navigate within the area covered by a VNC? Probably not a lot.
For those who have difficulties using a WAC, it is time to harden the 
up.