CXone Reporting API v2 agent state history query failing with 400

Why does the CXone Reporting API v2 endpoint /api/v2/reporting/agents/summary returns a 400 Bad Request when I apply a $filter for the last 24 hours using intervalStart and intervalEnd? I am constructing the OData query in Python with requests and passing ISO 8601 timestamps, but the response body indicates Invalid interval range despite the delta being exactly 86400 seconds. The payload looks like {'intervalStart': '2023-10-27T00:00:00Z', 'intervalEnd': '2023-10-28T00:00:00Z', 'intervalUnit': 'hour'}. Is there a strict alignment requirement for the intervalUnit granularity that I am missing?