A new preprint from the Hyper Suprime-Cam Subaru Strategic Program (arXiv:2605.18963, May 2026) leverages an unprecedented sample of approximately 3 million galaxies at 0.3 ≤ z < 0.7 and log(M/M⊙) ≥ 8.9 to demonstrate that galaxy structure depends on environment even after stellar mass is held fixed. The authors employ a mass-independent bulge-to-total ratio statistic, large-scale overdensity maps, and cluster catalogs, propagating structural posteriors via Monte Carlo sampling to achieve >5σ significance. At z < 0.5, structural trends appear only inside clusters, consistent with ram-pressure stripping and cumulative tidal encounters; at z ≥ 0.5 the signal extends to large-scale overdensities for massive systems while remaining cluster-confined for lower-mass galaxies. This redshift-dependent scaling implies that merger rates, group preprocessing, and cosmic-web stripping operated across broader spatial scales at earlier epochs than local-universe studies have captured. The work builds on the classic morphology-density relation first quantified by Dressler (1980) in nearby clusters and extends it beyond the smaller, lower-redshift samples of SDSS-based analyses (e.g., Bamford et al. 2009). Notably, the flat trends recovered when galaxies are split into star-forming and quiescent subsamples indicate that morphological transformation is tightly coupled to quenching, a nuance often obscured in mass-limited but environment-blind surveys. Because the paper remains a preprint, its structural-parameter measurements have not yet undergone independent peer review; photometric bulge-disk decompositions can also suffer from dust and viewing-angle biases that spectroscopic follow-up would mitigate. The findings suggest that next-generation wide-field missions such as Euclid and Roman will need to incorporate multi-scale environmental metrics rather than cluster-centric metrics alone if they are to model the assembly of the red sequence accurately.