Only if you cannot completely describe the geometry in the plan view of said pocket. The depth symbol works well for simple pockets. A section view removes all doubt, but for simple pockets, I don't think there is any, when the pocket is a basic profile extruded straight without draft.
Yes, I have a plan view of an irregularly-shaped flat-bottomed pocket without draft.
Wondering about creating a broken-out section around the feature (i.e. using a spline and showing hatch lines). Somewhere in the back of my mind I feel that I shouldn't dimension a line (even a visible line) that is not a part edge, without showing material x-section. Am I over-thinking it?
What do you need to dimension that isn't a part edge?
As others have stated, if the bottom is flat, just dimension the profile with a depth callout. I do parts with milled pockets frequently, and I only add section views if the bottom of the pocket needs special attention.