@Nanjundan Chinnasamy  Thank you for raising the document update request. Yes, there are few changes to permisisons required for Lead ads from Facebook. Currenlty the updates are in draft mode and we will be publishing these changes soon. FYI.. These are the complete set of permissions required for Leads ads. 

• leads_retrieval - Allows Paid Media Manager to retrieve the leads generated in Facebook.
• page_manage_ads - As per Facebook permission guidelines, the permission is used in parallel to the leads_retrieval permission. It is not explicitly used anywhere in Paid Media Manager.
• pages_show_list - To use lead ads, your Facebook app must be subscribed to the Facebook page. This permission is required for the subscription.
• pages_read_engagement - Required to subscribe the Facebook app to the Facebook page, and to retrieve the leads generated in Facebook.
• pages_manage_metadata - Required to subscribe Facebook app to the page, and for Facebook to send the leads to the Paid Media Manager service.

We will keep you posted once the document published. 

Thanks