How Clean Are Bell-Test Data? Classical Routes to S > 2, the Synchronisation Question, and an Auditability Standard

The reported violations of Bell inequalities are routinely read as an experimental refutation of local realism. This preprint asks how firmly the record supports that reading. We catalogue the classical routes by which a strictly local apparatus can report |S| > 2 - from outcome-dependent loss and coincidence-window selection (demonstrated in hardware) to synchronisation, electronics-level click shifts and analysis-parameter selection - and show that below the Eberhard efficiency the exact quantum correlation curve certifies nothing, being reproduced exactly by a known local detection model. We then define the first family-level synchronisation audit (plateau membership, bias index, sub-bound fraction), validate it on synthetic data with known ground truth, and execute it under preregistered protocols on three public archives. The raw Innsbruck record passes: across the full longdist series, every standard-configuration violation is a property of the raw data, not of the calibration. On the Delft event-ready data, a 50,000-member heralding-acceptance family answers the standing postselection critique: the violation is generic, not an acceptance choice. On the NIST 2015 record, an outsider reconstruction of the certified pipeline recovers the Bell geometry and gate optima but stalls at undisclosed cleaning parameters - a documented limit of third-party reproducibility. The programme distils into seven cleanliness criteria (C1–C7) for any dataset and eight provenance requirements (M1–M8) for future experiments. All figures and numbers are reproducible from the supplementary scripts (deterministic, fixed seeds, minutes on a laptop); raw data are fetched from the official public archives.