well maybe I don't have that right - I had been reading this:
P3102.1 Required vent extension. The vent system serving each building drain shall have at least one vent pipe that extends to the outdoors.
P3102.3 Size. The required vent shall be sized in accordance with Section P3113.1 based on the required size of the building drain.
P3113.1 Size of vents. The minimum required diameter of individual vents, branch vents, circuit vents, vent stacks and stack vents shall be at least one-half the required diameter of the drain served.
But your question made me find this:
P3109.3 Stack vent. A stack vent shall be installed for the waste stack. The size of the stack vent shall be not less than the size of the waste stack.
So unless I am getting tangled in definitions you are right...?
Btw, I am from your neck of the woods - enjoy the weather (esp in winter)
Thank you
John