Hello ravn;
Did you check the construction code, i.e., Section I, Section VIII, B31.3, etc.? The construction code will specify if CVN is required and whether PWHT is necessary for the thickness range being qualified.
The CVN is dependent on the construction code, the maximum thickness to be welded, and the lowest expected service temperature (including start-up and shut downs).
I can see situations where the thinner thickness range may not need CVN or PWHT, but the thicker material would need both CVN and PWHT if you are to list the full thickness range on your WPS.
There is more to qualifying the WPS than simply meeting the requirements of Section IX.
I always ask the client what construction code they will be working to so I can check for the "hidden" requirements that modify Section IX.
Best regards - Al