The first description gives the listener a mental image of surviving dwellings. The corrective balā then breaks that image and deepens the sense of desolation. The second utterance gains force by displacing the first.
Unlike ʿaks, which reverses an arrangement, rujūʿ reverses the assertive commitment of a prior statement. The two are not interchangeable categories.
Adding a second illustration without retracting the first is not rujūʿ.