Speech Discrimination and Rollover in CN VIII Pathology

A 52-year-old man presents with progressive unilateral sensorineural hearing loss (SNHL) over 6 months. Pure-tone audiometry shows moderate air-bone gap closure with a bone conduction threshold of 45 dB HL at 2 kHz. Speech audiometry reveals a word recognition score (WRS) of only 60% at 40 dB SL, but paradoxically improves to 75% when the presentation level is reduced to 30 dB SL. The structure marked **C** in the diagram represents a retrocochlear lesion of CN VIII. Which of the following best explains the disproportionately poor WRS and the paradoxical improvement at lower intensities observed in this patient?