Why does «كُلٌّ فِي فَلَكٍ» exemplify qalb?

Qalb, Tashrīʿ and Luzūm Mā Lā Yalzam: Completing the Verbal Ornaments

• Its letters ك ل ف ي ف ل ك are unchanged in reverse
• Its final two words share a pattern
• It admits two poetic rhyme endings
• It contains two forms from one root