Yeah, still no. Nowhere in the rule is anything saying the circle template is the base of the cylinder. Just that the cylinder has infinite height and is the size of (has a cross-section equal to) a circle template. The circle template doesn’t need to be the end of the cylinder to fulfill any of the rules at all, AFAIK. Usually it will be the end, since usually smoke will go down such that all of the template is at table height, or at least on a large rooftop, and that situation is reflected in the smoke diagrams. I’d love for CB to have included diagrams showing examples of smoke on stairs, ladders, or smaller roofs/raised surfaces.
What is a Smoke template? It is a ZVZ. What is a ZVZ? It is a Special Terrain zone. How is defined a Special Terrain zone? Like this: https://infinitythewiki.com/Terrain_&_Scenery_Structures Well defined area (the template specifically called out) and infinite height.