Risk to the writer: Low, if negotiated carefully
Far better than an undefined threshold, and still a warranty on a third party's software. It at least makes the obligation testable and bounded, and names the tool and the moment of measurement.
If you must accept a detector clause, accept this shape: named tool, stated threshold, measured at delivery, with a defined remedy of revision rather than non-payment.
General information, not legal advice. Have a solicitor or attorney review anything you intend to sign.