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It should update immediately if you're using direct query, but I think it only checks for data when you're interacting with things - e.g. it's not going to auto-refresh the page, but if you switched from one page to another it should update because it queries when the page loads or filters are applied.
Seeing immediate changes with the Power App visual in Power BI requires the source you're using to support direct query. Excel in OneDrive/SharePoint does not support direct query, so it will update along with your refresh schedule. You would be able to do this with a SQL or Dataverse source, though, for instance.