Offset between SPHERE and ALMA as a function of the ratio between the gas mass M_gas and maximum optical depth τ_max for all models from families F1 to F8 (i.e., all but F9). Models with different β_scale are shown with different symbols and colors. The dashed blue box shows the locus of models whose secondary belt is brighter than the birth ring in the SPHERE radial profiles. The underlying contours show a 2D KDE for all the models. A secondary x-axis at the top shows the estimated gas to dust mass ratio.