When performing the initial synchronization of a new automation, no records are detected, even though one was created after the automation was created.
Under normal circumstances, when an automation is running, it's going to take the end time of the previous run and use it as the start time of the current run. But the first time an automation is run, it doesn't have that reference, so to "bootstrap" itself, it uses the current time as the start and end time, as shown here in the logs:
Count of modified records from <source> found since 'Thu Jan 30 15:45:46 UTC 2025' till 'Thu Jan 30 15:45:46 UTC 2025' is :0
This is behavior is working as designed and any records created after the initial automation run should synch as expected.