Comparisons between the differences between the true v_los and the predictions of our methodology and Naik24, with samples decomposed into different halo substructures. We include all stars from the true groups, plotted with triangles, and true likely members with membership probability greater than 50%. Only groups with more than 4 likely members are plotted. The points and error bars represent the median and the 16% and 84% percentiles of the distribution, respectively, for the likely groups. These results use the crossmatched 6D sample described in the main text.