A passage may contain multiple rhetorical operations: one element may be omitted for concision, while another is expanded for clarification or emphasis. A global judgment about the whole expression is still relative to its total intended meaning.
For instance, «والصلاة الوسطى» highlights one member after a general class, while other parts of the same verse may be economical. The rule concerns a particular addition, not necessarily every word in the passage.
A strong analysis identifies the exact site of omission or expansion and then explains its distinct effect.