Calling List Sessions results in a 405 error

https://docs.liveavatar.com/reference/list_sessions_v1_sessions_get

I'm trying to list active session IDs using the API Reference above, but I'm getting a 405 error (Method Not Allowed) and can't retrieve them.
The GET method requires a body, so Javascript and Google Apps Script force me to send it as a POST.
Would it be possible to support X-HTTP-Method-Overrid or a query string?