V2.analytics.conversation.aggregate event payload parsing issue

Docs state: “The payload contains a nested data structure with conversation details.” My consumer hits conversation.created fine, but the analytics aggregate event throws a TypeError: Cannot read properties of undefined (reading 'duration_ms').

Here’s the relevant snippet:

const event = req.body;
const duration = event.data.conversation.duration_ms;

The console shows event.data is an array, not an object. Why is the structure different from the standard event docs?