This work presents a minimal, falsifiable test of a coherence-modulated growth extension motivated by the Sympathetic Harmonic Resonance Framework (SHRF) and the Toroidal Coherence Principle (TCP), evaluated against the Dark Energy Survey Year 6 (DES Y6) 3x2pt consistency metrics. The analysis follows the DES Y6 methodology exactly for quantifying parameter differences between low-redshift large-scale structure measurements and primary CMB constraints (Planck 2018 + ACT-DR6 + SPT-3G DR1), using the same parameter-difference probability distribution and effective n_sigma mapping based on normalizing flows. The proposed extension modifies the linear growth equation via a late-time, scale-dependent rescaling of the effective clustering strength, recovering LCDM in the zero-amplitude limit. Consistency is evaluated both in the full shared parameter space and when projected onto the derived parameter S8. The framework is explicitly designed to be measurement-first and falsifiable: the model is disfavored if tension reduction occurs only through extreme nuisance parameter shifts, induces conflicts with independent growth probes, or is penalized by model selection criteria. This work does not claim resolution of cosmological tensions, but instead provides a controlled test of whether late-time coherence effects can account for the observed DES Y6 parameter differences within an internally consistent statistical framework. cosmology, large-scale structure, Dark Energy Survey, S8 tension, growth of structure, modified gravity, coherence, parameter consistency Theoretical analysis IsSupplementTo: DES Y6 3x2pt cosmology analysis