General relativity in a ΛCDM background fixes the growth index at gamma = 0.55: structure must grow at the rate f(z) = Ω_m(z)^0.55. Nguyen, Huterer and Wen (2023) measured gamma = 0.633 +/- 0.025 from combined growth probes, excluding the GR value at 3.7σ, rising to 4.2σ with Planck fsigma8. Late-time structure growth is suppressed relative to the model, and letting gamma float also absorbs the Planck lensing-amplitude anomaly, tying the two excesses together.
The assumption is that every dynamical and lensing signal at late times is produced by matter alone growing under GR with a constant Λ. The growth history then has no freedom, so when the sky shows a different late-time amplitude than the early-universe normalization predicts, the fit must bend a parameter the model says is fixed, and gamma jumps off its GR value.
SCT replaces the hot-dense-center with a superluminal collision, and replaces the bare matter field with coherently superposed comoving sources whose amplification grows as structure virializes (P50, P52). The inferred clustering amplitude scales as sigma8_inferred = A^(1/2) x sigma8_true (Paper 6, Equation 20), and A(z) climbs from 1 before structure exists to 5.85 today, tracking the virialized volume fraction. An early-universe normalization evolved forward under GR-plus-matter-only therefore overpredicts the true late-time clustering, and a fit parameterized by gamma absorbs the shortfall as apparent growth suppression: gamma rises above 0.55 exactly when the mesh contribution becomes significant, in the dark-energy era.
The crucial point is that gravity is never modified: SCT predicts no departure from standard gravity at late times, and the apparent suppression is an accounting artifact of attributing coherence amplification to matter growth. That is why the same data that prefer gamma = 0.633 also prefer A_lens above 1, and why floating either parameter relieves the other: they are two projections of one unmodeled coherent term. GR is recovered exactly in the N = 1 limit (P53), and the Bianchi identity holds throughout.
This is the same coherence signature behind the S₈ deficit and its low-redshift kink, the lensing-amplitude anomaly, and the closed-universe pull. There is no need to invoke modified gravity, which generically predicts enhanced rather than suppressed late growth, nor neutrino masses that the data independently cap.
Two registered kills. First, the redshift shape: the apparent suppression must weaken with redshift as A(z) falls toward 1; if Euclid and Rubin-LSST find the gamma excursion equally strong when measured from high-redshift growth data alone, the superposition reading fails. Second, a statistically significant detection of genuine late-time modified gravity inconsistent with GR, surviving marginalization over lensing amplitude, would falsify SCT's claim that the gravity sector is standard at late times.