What is the proper scholarly caution when examining a phrase such as “salāmun ʿalā il-yāsīn”?

Division of Surahs into Verses, Qur’anic Rhythm, and Verse Endings

• Replace the wording without considering context
• Use it to claim that Arabic grammar is irrelevant
• Classify it automatically as one poetic ziḥāf
• Consider its wording, recitation, Arabic usage, and context