Binding an attached property instance to a Connection.target results in attachee being set as a target

TextField {
    id: tf
}

// error: qrc:/main.qml:24:5: QML Connections: Detected function "onReturnPressed" in Connections element. This is probably intended to be a signal handler but no signal of the target matches the name.
Connections {
    target: tf.Keys
    function onReturnPressed() {
        tf.text = "<Return>";
    }
}

// error: qrc:/main.qml:34:5: QML Binding: Property 'Keys.onReturnPressed' on TextField is read-only.
Binding {
    target: tf
    property: 'Keys.onReturnPressed'
    value: (event) => {
        tf.text = "<Return>";
    }
}

Connections {
    id: con2
    target: tf

    // there's no syntax for arbitrary function names in JavaScript
    //function `onKeys.ReturnPressed`() {
    //    tf.text = "<Return>";
    //}

    // `Symbols as function names` aren't supported in QML in such form either.
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name#symbols_as_function_names
    //[Symbol("Keys.ReturnPressed")]: {
    //    tf.text = "<Return>";
    //}

    Component.onCompleted: {
        // error: qrc:/main.qml:41: TypeError: Value is undefined and could not be converted to an object
        con2.__prototype__[Symbol("Keys.ReturnPressed")] = () => {
            tf.text = "<Return>";
        };
    }
}

property var keyz: tf.Keys
onKeyzChanged: print("keyz =", keyz, ", tf.Keys =", tf.Keys);
// qml: keyz = QQuickKeysAttached(0x561fbedff360) , tf.Keys = QQuickKeysAttached(0x561fbedff360)