The BI Connector does not write any data to Oracle Applications. It only fetches the required Oracle data and sends it to your preferred data visualization platform, say Power BI or Tableau.
The connector however requires write permission to create (and delete) reporting objects in the reporting layer of Oracle Fusion applications. The reason for requiring this write permission is for processing the filters applied in the data visualization platform and for data chunking.
For example, if a user connects Power BI to a Data Model residing in the /shared/Custom/Financials path and applies a filter condition in Power Query Editor, the BI Connector would not modify the query of the existing Data Model object for processing the filter, as doing so could impact other users who rely on that Data Model. Instead, the BI Connector creates a new Data Model with the modified query to process the filter and deletes the new Data Model it created automatically once the data is fetched. Further, the write permission is also required to develop Data Model queries from within the BI Connector.