In al-qatlu anfā li-l-qatl, the unqualified word “killing” can appear to suggest that any killing prevents further killing. Unlawful killing, however, may cause retaliation and more violence.
Al-qiṣāṣ avoids that overbreadth by referring to a regulated response to a specific wrong, within established conditions. A single accurate term performs more precise work than an unqualified generic term. Semantic precision matters to concision as much as brevity does.