Difference between the true and fitted M_★ for SPHINX²⁰ galaxies at z = 6 when the normalised true SFH model is fitted with intS_Z_true. Using BC03 template is used (red) yields systematically larger M_★ values than BPASS (blue). This offset arises because BC03 predicts lower rest-frame optical fluxes than BPASS, even under the same SFH is used. The inset presents an example SED fit with both templates, with the x-axis showing to observed wavelengths from 0.9 to 5.0 microns.