إِنَّمَا وُجِدَ الْخَلَلُ فِي الْمِيزَانِ الْأَوَّلِ، لَا فِي الثَّانِي.
The fault was found in the first scale, not in the second.
Imagine a separate pair of scales where the listener confidently alleges the second alone was defective. Correcting that allocation reverses the listener’s position: qaṣr al-qalb. This hypothetical comparison is independent of the two faulty scales in the base inspection, avoiding a contradiction in the case facts.
A restriction particle does not by itself classify the case. The listener’s prior belief and what the reply corrects determine whether the rhetorical effect is reversal or mere exclusion.