The person sanding knows that looking smooth and feeling smooth are different achievements.

The eye is easily satisfied and the hand is not. A surface can look finished under good light and still catch on every pass, and the only way to know is to touch it, which is a slower and less flattering test. Anyone who has done that work stops trusting appearance as a measure of quality.

Wherever you can, use the test that involves contact rather than the one that involves looking. Read the document aloud, walk the route, try the process yourself instead of reviewing the diagram. What you find will be less encouraging than the appearance was, and it will be the thing your users meet.