What chiefly separates tatmīm from iḥtirās?

Supplementary Practice 1: Applied Analysis of Faṣl, Waṣl, Ījāz and Iṭnāb

• One is confined to past and the other to present tense
• Tatmīm contains no addition
• Iḥtirās must occur at the end of poetry
• Tatmīm enriches the point; iḥtirās blocks an unintended inference