This action is taking the run_started_at (second precision) from the /repos/{owner}/{repo}/actions/runs/{run_id} api and then waiting for only strictly older workflows to finish. If one runs multiple workflows in a single second, they all output only e.g.
searching for workflow runs before Tue Apr 16 2024 13:03:54 GMT+0000 (Coordinated Universal Time)
found 0 workflow runs
no active run of this workflow found
and continue concurrently.