True flux vs redshift for key emission lines in the mock EDS-SF_sim (top) and EWS-SF_sim (bottom) samples. Contours in dark green, light green, blue, orange, and red correspond to Paβ, Hα, [N II]λ6584, [O III], and Hβ, respectively, selected to span a broad redshift range and wavelength coverage. Each line’s redshift range reflects its detectability within the grism coverage. Contours from lighter to darker shades trace the 99th, 84th, 50th, 16th, and 1st percentiles of the distribution. Grey areas mark fluxes below the survey sensitivity limits.