Projection effect of the TNG-100 ETG sample. Each ETG is projected 4 times onto random directions (blue and coral histograms). Each dot in the 2D histograms represents a projection. We apply a lensing cross-section weighting proportional to θ_E², as represented with the green and purple histograms. We model the lensing selection on the projected ellipticity e, showing that for the oblate sample, lensing selection favors more elliptical galaxies in projection, while for the prolate sample, the lensing selection favors rounder galaxies. For the oblates, the viewing angle θ equals the inclination angle i for pure oblates, and thus under lensing selection cos θ is also inclined to the lower end, i.e., towards higher inclination angles and consequently higher ellipticities. The “bias” in the kinematics under the assumption of SIS lens models b_σ = σ_SIS/σ_rm − 1 is labeled with dashed lines. The mean bias ⟨b_σ⟩ for the oblate sample, indicated with blue dashed lines, is directly under the coral dashed line representing ⟨b_σ⟩ for the prolate sample and thus invisible from the plot.