Whether the CSV is updated in real time depends on the Export Mode selected in the automation settings:
Limited export with real-time data: The CSV is generated with current Airtable data each time the export URL is opened. This mode includes up to 2,000 records.
Scheduled, complete export: The export URL returns the most recently generated cached CSV. The file is generated by hitting the 'generate now' button. This mode is intended for complete exports that may contain more than 2,000 records.