«وَلِصَاحِبِ عِلْمِ الْمَعَانِي فَضْلُ احْتِيَاجٍ إِلَى مَعْرِفَةِ الْجَامِعِ»
A student of ʿilm al-maʿānī has a particular need to recognize the unifying relation.
Many judgments about faṣl and waṣl turn on the connection between clauses. Rational links are important, but contrasts apprehended through estimation and associations formed through imagination also demand attention because they depend on audience experience.
A conjunction is not rhetorically justified by syntax alone: it should express a fitting semantic relationship under the circumstances of the speech.