In the OAuth2 Guide https://backstage.forgerock.com/docs/am/6.5/oauth2-guide/#rest-api-oauth2-device-code the OAuth2 device flow shows it supports draft https://tools.ietf.org/html/draft-ietf-oauth-device-flow-03
This is further established within AMs code
This showing that the response_type parameter is a requirement for authorization requests.
In the latest draft https://tools.ietf.org/html/draft-ietf-oauth-device-flow-15 it shows that this parameter is no longer a requirement
– o response_type parameter removed from authorization request.
The RFE is for AM to support the latest device flow draft '15' so that the response_type parameter is no longer required.