Faṣl and waṣl regulate relations between clauses; ījāz conveys the intended meaning economically; iṭnāb expands language for a discernible gain; and musāwāt maintains a proportionate expression. All ultimately serve accurate and effective communication.
A sound judgment considers the amount of wording, syntactic structure, and the communicative objective together. More important than recalling a technical label is explaining, with evidence, what the particular choice achieves.