Tableau Connector Pro for Jira, uses OAuth protocol to access Jira Rest API on behalf of the users. The add-on never asks for a user's Jira credentials. All the calls to the Rest API are made using OAuth authentication and the data returned by Jira is governed by the access permissions of the user whose OAuth credentials were passed in the request.
Every user gets their own unique URL via Jira > Tableau Connector Pro > My Connectors menu. The data returned by this unique URL is restricted by the Jira permissions for the user to whom the URL belongs.
The token at the end of each URL is different for each user and maps to the OAuth credentials, which are passed to the JIRA rest API with each request to fetch the data.