What principally separates iqtīḍāb from takhalluṣ?

Iqtibas, Tadmeen, Aqd, Hall, Talmih and the Art of Literary Openings and Endings

• They are always identical
• Iqtīḍāb need not provide an explicit semantic bridge
• Iqtīḍāb is only a rhyme scheme
• Takhalluṣ has no change of topic