@slbaumgartner said:
Out of curiosity, did you try showing hidden geometry to see whether that face was split by a non-visible line already?
Yeah, that's how I verified the direction I should use when drawing the line.
As I said before, this wasn't an issue using the FollowMe tool, it was the Upright Extruder. The product of both functions look identical in the middle of the extrusion; FollowMe along an Arc screws up at both ends, the Upright Extruder gets the start correct by has the same flaw at the end. You would not know the faces in the middle were actually quite different in the results of each function until you started texturing.