This is Jesse from the Statuspage support team. For this I would point you here to the status embed help page: https://support.atlassian.com/statuspage/docs/what-is-status-embed/
It mentions the following:
The status embed for maintenance is shown 24 hours prior to the maintenance occurring and during ongoing maintenance, until the page viewer closes the status embed flag.
Please let me know if you have any other questions around this. I hope you have a great day!