Posterior predictive check: cumulative distribution functions (CDFs) of the observed secondary-mass distribution for the MLTP, MLTP-paired, PS-paired, and Flexible-BBH models. Shaded regions (dashed lines) represent the observed (predicted) event distributions. All bands indicate 90% credible intervals. The observed band from the MLTP model lies slightly outside the predicted region, indicating its weakness relative to the other models. The Flexible-BBH, PS-paired, and MLTP-paired models provide a better fit than the truncated model as their shaded regions overlap entirely with the dashed bands owing to their greater flexibility in capturing additional features in the secondary-mass distribution.