Top: number of retained star clusters when clusters older than a particular age limit from the catalogs of Nayak et al. (2018) and Piatti (2018) are excluded. Middle: significance of the BeXRB–closest cluster distance bimodality as obtained from a two-sample Anderson-Darling test with respect to the applied age cutoff. The horizontal dashed line indicates the classical significance threshold of p = 0.05. The p-values that exceed 0.25 need to be considered as approximate because they are computed by extrapolation. This threshold is indicated by the horizontal dotted black line. Bottom: effect size of the bimodality quantified using Cohen’s d as a function of the applied age cutoff.