Cosmological parameters derived from the abundance of galaxy clusters often conflict with those derived from the primary CMB. Specifically, the number of observed massive clusters is lower than predicted by the Planck CMB best-fit cosmology (related to the S8 tension). A key suspect in this discrepancy is "hydrostatic mass bias": the possibility that X-ray and Sunyaev-Zeldovich (SZ) mass estimates—which assume gas is in hydrostatic equilibrium with the cluster's potential—systematically underestimate the true cluster mass. Simulations suggest non-thermal pressure support (turbulence, bulk motions, magnetic fields) could cause a bias of 10-20% (b ~ 0.2), but reconciling the CMB and cluster counts might require an implausibly large bias or new physics suppressing structure growth. The tension questions whether our understanding of cluster astrophysics or the underlying cosmological model is incorrect (Planck Collaboration 2015; von der Linden et al. 2014). SCT must explain why cluster mass estimates might be biased or why structure growth is suppressed without invoking dark matter properties.