Genesys Cloud Web Messaging: Sending typing indicators via Guest API

POST /api/v2/conversations/messaging/participants/{participantId}/typing
Returns 405 Method Not Allowed. I am trying to send typing indicators from my local Docker Compose test harness using the Guest API.

{
 "eventType": "typing"
}

The documentation mentions read receipts, but I cannot find an endpoint for typing status. Am I missing a specific header or is this unsupported?