Comment 7 for bug 1982183

The lockscreen inhibitor is only active as long as the u-r-u process is. This is probably why the issue is more apparent with the non-interactive frontend, because it will exit silently, whereas the text frontend would prompt the user to reboot (and many users would just accept).

IIRC the D-Bus service invalidates the inhibitor after the calling process exits, so I don't think there is anything u-r-u can do to ensure the inhibitor stays in place after it exits.