How to set up a rollup field using the API?

According to the API docs, it should be possible to set a rollup field using the REST API.

However, if I send this:

{
    "name": "Total Points",
    "description": "Automatically calculated total points for each user",
    "type": "rollup",
    "options": {
        "fieldId": "fld...", // Field ID of a "Points" field in a Points table
        "linkedTableId": "tbl...", // ID of the Points table
        "aggregation": "SUM"
    }
}

I am getting this error:

{
    "error": {
        "type": "UNSUPPORTED_FIELD_TYPE_FOR_CREATE",
        "message": "Invalid options for Leaderboard.Total Points: Creating rollup fields is not supported at this time"
    }
}

I asked ChatGPT and it tells me that rollup fields cannot be created using the API, despite the API docs claiming otherwise. Is this true, or am I doing something wrong here?

(Setting up the rollup field using the UI works just fine.)