Rujūʿ is a purposeful retraction or reversal of an earlier statement for rhetorical effect. It is not merely an accidental contradiction.
«قِفْ بِالدِّيَارِ الَّتِي لَمْ يَعْفُهَا الْقِدَمُ بَلَى وَغَيَّرَهَا الْأَرْوَاحُ وَالدِّيَمُ»
“Stop at the dwellings which time has not effaced—rather, winds and prolonged rains have transformed them.”
The initial impression of preservation is deliberately overturned by balā, making the sense of decay more forceful.