I asked rhetorically (and didactically) for the benefit of anyone reading this topic
The technically correct line where the turned cone meets the square post is a hyperbola. When the curve is very shallow, as Shep drew (a very broad cone), a circular arc can approximate it fairly well. But if the cone is more steeply tapered, at what point is the circular arc no longer “close enough”? You really can’t tell unless you generate the hyperbola. There is no way to do so using built in tools, but the follow-me plus intersect method does it as quickly and accurately as SketchUp is capable of.
Of course, as Shep illustrates, once you have the technically correct curve you can use sandbox to fill in between it and the center circle if you prefer triangulated surfaces vs quadrilaterals.