Okay, I think 6a0f1f6d5af7c7300d3db7a0ba2b068f8abd222b "sd-event: rework API to support CLOCK_REALTIME_ALARM and CLOCK_BOOTTIME_ALARM, too" removed the dual_timestamp_is_set assert. It looks like it was fixed by accident, and there's zero acknowledgement that flooding /dev/kmsg could be a problem on systemd's side.