إِنَّمَا اخْتَلَّ الْمِيزَانُ الْأَوَّلُ فِي هَذَا الْفَحْصِ.
Only the first scale proved faulty in this particular inspection.
In a separate inspection, suppose the listener believes both the first and second scales proved faulty. The statement removes the supposed second participant rather than reversing the entire allocation; that is qaṣr al-ifrād. Reversal corrects an opposed allocation, while ifrād excludes a presumed co-participant.
Thus a formally similar expression can have a different category when the audience’s previous belief changes. The local context must be fixed before classifying it.