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Semianalytic models (SAMs) systematically predict higher-stellar mass scatter at a given halo mass than hydrodynamical simulations and most empirical models. Our goal is to investigate the physical origin of this scatter by exploring modifications to the physics in the SAMDark Sage. We design two black hole formation models that approximate results from theIllustrisTNG 300-1hydrodynamical simulation. In the first model, we assign a fixed black hole mass of 10⁶M_⊙to every halo that reaches 10^10.5M_⊙. In the second model, we disregard any black hole growth as implemented in the standardDark Sagemodel. Instead, we force all black hole masses to follow the medianz= 0 black hole mass–halo mass relation inIllustrisTNG 300-1with an imposed fixed scatter. We find that each model on its own does not significantly reduce the scatter in stellar mass. To explore the effects of active galactic nucleus (AGN) feedback in addition to black hole seeding, we replace the native Dark Sage AGN feedback model with a simple model where we turn off cooling for galaxies with black hole masses above 10⁸M_⊙. With the additional modification in AGN feedback, we find that the supermassive black hole seeding and fixed conditional distribution models create a significant reduction in the scatter in stellar mass at halo masses between 10^11–14M_⊙. These results suggest that AGN feedback in SAMs acts in a qualitatively different way than feedback implemented in cosmological simulations. Either or both may require substantial modification to match the empirically inferred scatter in the stellar mass–halo mass relation.