I compared the ambient magnetic noise in the O4b (evaluated the Hamamatsu lightning as a PEM injection) to the target sensitivity of the O4b (10Mpc) and the O5a (37Mpc) shown in JGW-G2415922 by Komori-san.

This result shows that ambient magnetic noise can be a serious noise in the O5a.
Note that this evaluation used a transient noise and was not so precise. So we need to investigate more via magnetic injection tests.