Function iceberg_update_mode 

fn iceberg_update_mode(
    with_properties: &BTreeMap<String, String>,
    refresh_mode: &Option<SourceRefreshMode>,
    rate_limit: Option<u32>,
    row_id_index: Option<u32>,
    stream_kind: StreamKind,
) -> StreamResult<bool>

Whether the List and Fetch executors of an Iceberg source run in streaming update mode. Both read the same plaintext option, so they cannot disagree on the mode.