Cluster outskirts hold uniform metallicity beyond 500 kpc, flat profiles requiring the gas enriched before it fell in, pre-processed to a common level across regions that had never shared a structure (Leccardi and Molendi 2008; Mernier 2017). Hierarchical assembly predicts the clumpy central injection the data rule out, and its early universe has too few stars too late.
Metals in the model are made by stars formed after halos assemble and spread by mixing afterward, a sequential clock that delivers enrichment late, local, and lumpy. Early-and-everywhere uniformity inverts all three properties, and no feedback prescription transports metals backward in time.
SCT's enrichment clock starts where its star formation does: at deposition. The first stellar generation ignited early and nearly simultaneously across the structure-bearing web, on dense collision-seeded reservoirs (P22, P25, P34), and completed fast, the same accelerated chemistry that lays the universal metallicity floor (recid 125) and delivers oxygen-rich galaxies at z above 14 (recid 113). The gas that would later fall into clusters was therefore enriched before cluster assembly as a matter of course: pre-processing is not a special mechanism but the default consequence of enrichment and future structure sharing the same deposited geography. Flat outer profiles at a common level are the fingerprint of that shared early bath, and the shallow central gradients follow as ordinary late injection layered onto an already-uniform base.
The chemistry stays honest under the usual bookkeeping: the cascade erased prior nuclei above the QCD scale, so the metals are in-cycle products of the fast first generation, not inherited (P40, P42). The registered expectation travels with the timing: outer-region metallicity should be uniform at ever-larger radii as X-ray surveys push outward, and its level should connect quantitatively to the floor abundance the earliest enrichment laid down, the two measurements bracketing one early epoch. The seeding mechanics are in Paper 4, From Chaos To Collisothermal Cosmogenesis.
Keystone economy: P25 fuels the early generation, P34 spreads it everywhere structure would later stand. The metals were waiting for the clusters, not the reverse.
The kill follows the uniformity: Athena-class profiles finding the outer metallicity clumpy and declining at the largest radii, consistent with late localized injection plus mixing, would restore the sequential clock and make pre-enrichment unnecessary. The timing half cuts with the family: high-z absorption measurements finding the proto-cluster gas unenriched at epochs where SCT's first generation should already have processed it would break the early-and-everywhere reading alongside the metallicity-floor sector.