What most clearly distinguishes iḥtirās from tatmīm?

Supplementary Practice 5: Textual Analysis, Scope of Meaning and Rhetorical Judgment

• Iḥtirās blocks a likely misreading; tatmīm adds useful completion
• Iḥtirās is always one word, tatmīm always two clauses
• Both merely alter rhyme
• Tatmīm necessarily contains a negation