Iṭnāb (الإطناب) adds wording for a purpose such as emphasis, explanation, specification, warning or prevention of a misunderstanding. Unhelpful length is not eloquent expansion.
The terminology distinguishes:
Taṭwīl (تطويل) — pointless lengthening where identifying one distinct dispensable portion is difficult.
Ḥashw (حشو) — an identifiable unnecessary insertion, whether merely superfluous or meaning-distorting.
Ikhlāl (إخلال) — compression that leaves essential intended meaning unexpressed.
Both concision and expansion are judged by whether they preserve and serve the intended meaning, not by their size.