When Do Cross-Modal Gains Warrant a Semantic Role? A Role-Conditioned Audit of Derived Pairing Rules

Cross-modal gains can change learning, but they do not by themselves show that the assigned relation explains the gain: a nuisance scaffold can reproduce the same endpoint pattern. The cross-modal alignment spuriousness (CMAS) audit makes this premise-failure gap explicit through three layers: phenomenon (whether a gain is observed), mechanism (which information and computational routes are active), and boundary (whether nuisance-relative utility clears declared margins). In a five-seed DOLOS case restricted to one corpus, carrier/backbone, split, and validation-only known-offset endpoint, the primary provenance–time contrasts are inconclusive at the declared margins, while phase is recoverable but phase-selected directions do not outperform rank-matched random subspaces. A second same-carrier role is likewise not authorized at this scale. The operational conclusion is bounded: cross-modal gains can change learning, but they do not by themselves authorize the assigned semantic role beyond declared alternatives.