Proportionate clause length helps sajʿ sound balanced. Equal or nearly equal lengths often create coherence. A somewhat longer second unit is not always defective, but a severe imbalance can weaken the relation heard between the endings.
Muraṣṣaʿ especially benefits from parallel ordering of internal expressions; muṭarraf and mutawāzī rely on the closing words together with reasonable proportionality.
When an excessively long passage intervenes before a very short conclusion, the first ending may fade from the listener’s ear. Balance, clarity, and effect therefore matter together.