Hello Girish,
I could not find much in the official docs. The formDefinitionId field does exist in the role schema (V3 API spec & spec), and the description even says the form should be presented to the requester during the access request process. So your config looks right.
But I don’t think this is a live feature yet. SailPoint had this in discovery back in mid-2024, and as of August 2025 their product team said it was still a future project with nothing scheduled. From what I can tell, the API accepts the value without error, but I think the Request Center just doesn’t pick it up. Maybe the schema is ahead of the UI on this one.
I would suggest that you check the In Discovery: Forms in Access Requests thread for any recent updates or reach out to Jennifer Mitchell (the thread owner from SailPoint PM) directly.