Your drawing shows a confusion between sweeping and smoothing. You can scan a profile to which you give a fig 1,1B trajectory. But smoothing (2 different profiles) is a gradient of an open or closed profile to another profile figure 2A (or even a point fig 2). Only after smoothing (Fig 2b) may be added to smooth scanning guide curves (Fig 5.5A) or directions (Fig 4).
Better generally make a different sketch for each curve or profile used.
Smoothing is prefered to limit surface that
SWEEP TRACK ALONG
SWEEP TRACK ALONG WITH CONSTANT NORMAL
SMOOTHING TO A POINT
2 PROFILE FOR A SMOOTHING
SMOOTHING WITHOUT GUIDE LINES
SMOOTHING WITH ONE GUIDELINE
SMOOTHING WITH 2 GUIDELINES
A surface smoothing is preferable to a border area used primarily for closing the meeting of several surfaces cà their borders.