Ratio between the internally calibrated spectra of each of the Gaia SAs and Hyades 64 in the blue photometer (BP, left panel) and the red photometer (RP, right panel). We also plotted the ratio of the mean Gaia SA and Hyades 64 (black solid line) and the binned version of this ratio at the wavelengths provided for SSO in Gaia DR3 (black dots). ¹ We note that the star identified as 16 Cygnus B in Gaia Collaboration (2022) is in fact 16 Cyg A (see the main text for more details).