Is the iSRD function not available on B/W film?

Plustek Original FAQ Link

iSRD can be used with conventional color negatives (developed using the C41 process), color slides (developed using the E6 process) and paper proofs. Due to the silver content in conventional black and white negatives and slides, these can’t be retouched using iSRD.

SilverFast official post:
https://www.silverfast.com/about-silverfast-why-scanning-basics-of-scanning/why-silverfast/silverfast-feature-highlights/isrd-dust-scratches-removal-eliminate-defects-with-infrared-channel/

Black and white film: Black and white film is another special case in terms of dust and scratch removal. Unlike color slides or color negatives, the scanner’s infrared rays can not permeate through the film emulsion, due to the silver halide layer contained in the film. This means that infrared based tools like iSRD, ICE, FARE or MagicTouch can not be used here.