The discussion of the best sajʿ puts meaning before sound. If a speaker predetermines an ending and bends every sentence unnaturally to reach it, the rhyme becomes artificial and weakens eloquence.
Good sajʿ chooses expressions for the subject, meaning, and occasion; the harmonious ending then sounds like a natural result of apt diction.
This is more than a matter of taste: replacing a precise word with an awkward one merely to preserve sound can reduce clarity and force.