@Piotr Butyński Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
Firstly Apologies for the delay response,
Files are tiered based on the last access time in the heatstore database. If you don't want to wait for the files to be tiered because they were recently accessed by AV and Backup, they can manually tier the files using the Invoke-StorageSyncCloudTiering cmdlet: How to manage Azure File Sync tiered files | Microsoft Learn
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