This depends on what type of connection you have with Xero.
If you only turned on Bank feeds sync, we won’t have access to any sensitive information from Xero about your transactions, or other financial data. To sync your Wise transactions to Xero, we only need to know your account information and the details for each currency account you have activated.
If you turned on Import bills to Wise, we'll access all bills you've created in Xero, so you can pay them through Wise. This will mean we have access to that data.