wrapUpCode null in /api/v2/analytics/details despite valid response

Pulling call details via POST /api/v2/analytics/details. The wrapUpCode field is consistently null across all records. Docs state: “The wrap-up code assigned by the agent.”

Payload:

{
 "viewId": "calls",
 "interval": "2023-10-01T00:00:00.000Z/2023-10-02T00:00:00.000Z",
 "groupings": ["wrapUpCode"]
}

200 OK returned. 15 years in OAuth, this feels like a bug. Why is it null?