Sketching is a core theme for Spaces and allows for extremely quick and effective input. Sketching is incredibly powerful and we see huge potential in how to improve sketching and continually make it smarter.
At the moment Spaces works best when sketches are unambiguous and can produce a single clear result.
For example the following sketch provides a variety of possible outcomes because multiple polygons are defined:
Therefore to provide a clear outcome, you should use the Squiggle to clean up the sketch:
Creating a clean building outline:
The same applies when editing Face contours:
Cleaning up the top stroke you create a clear contour