There are some cases where job dispatching too close to startup can cause operation failures.
If Opencast restarts, the proxy (e.g. apache) can mark the service as offline and requests get a service-not-available 503 error for a short time even after the service has come back, because the proxy has a timeout, as described for the try parameter here:
So Opencast checks for available services on http://server.domain/ and gets back nothing available even though it's up.
So it is safer to add a delay before starting to dispatch jobs on startup. This is most significant for scenarios where Opencast admin node is restarted while workflows are running (usually for unplanned reasons), and avoids workflows failing because no services are available.