Dataset returned by system.eam.queryAgentHistory

I have some questions regarding the dataset returned from system.eam.queryAgentHistory, and I haven't found any documentation about the possible values returned for each column.

According to the documentation, this function will return a dataset with columns id, agent_name, agent_role, event_time, event_category, event_type, event_source, event_level, event_level_int, and message, where each row is a new agent event.

When I run this in the controller, every row returned has 'Unspecified' for the agent_role column, and None for the message column:

agent_role: Unspecified
message: None

Where are these values coming from? I haven't found any settings in the controller or agent gateways related to these columns and I'm wondering where/if I can set the agent_role and understand why nothing gets returned for the message column?

'Agent_Role' will be one of "Unspecified", "Master", or "Backup", depending on the redundancy role of the agent gateway.

I only see one code path (currently) where the message will be populated:
"Disconnect requested by agent."