While I generally agree, these symbols are mostly obsolete or at least don't apply to embedded solutions.
I end up using process and decision. The rest don't have much meaning for my projects.
Personally I put the shape of the symbols much lower than the flowchart logic and content. If I were teaching I would focus on how a flowchart can help you write a better program. Perhaps see approaches that may not have been obvious when you started, not which symbol shape is proper.