Scope-Indexed Law Discrimination in Relational Quantum Cosmology: Actualized Data, Reachability, and Class-Restricted Fibres

A realized cosmological history need not uniquely identify its dynamical law. This paper formulates that statement operationally for relational quantum cosmology by distinguishing actualized records, physically reachable internal responses, and modal host responses. For finite second-order linear hosts it relates realized-history spans to Krylov/module-generation structure and separates carrier-generation thresholds from law-identification thresholds through class-restricted residual fibres. The framework is then specialized to source-native group-field-theory cosmology, including finite Fourier carriers, symmetry-induced degeneracy, interaction-induced carrier breakdown, non-autonomous tangent systems, physical readout limitations, and a source-exact prospective nonintersection test. The central boundary is between mathematical discrimination available in the host and discrimination physically instantiated by the declared relational contract.