DM_ext distribution. The same color scheme is used as in Figure 3, except that the CHIME Catalog 2 DM_ext distribution is shown by the solid black histogram. For each detectable synthetic event, DM_ext is assigned using DM_ext(z) distribution, and the same DM_ext selection in Section 2.1 is applied. The horizontal axis is linear, whereas K. Shin et al. (2023) and CHIME/FRB Collaboration et al. (2026) use a logarithmic axis. Probability densities in the two coordinates are related by ﹩p(x)=p(\mathrm{log}x)/x﹩. We use a linear axis because DM_ext is approximately a linear proxy for redshift.