No. As of now, Core does not support real-time syncing of records. If you make changes to records in Core that you have synced with QuickBooks Online, you need to sync them again to update them there or do that manually. You also need to make sure that the option If record exists, overwrite is not set to Never in QuickBooks Sync Detail > Sync Settings > Send. Otherwise, the record does not update. Check the Core Help for details.