[REG 6.6->6.7] TypeError: Property 'onDownPressed' of object QQuickKeysAttached(...) is not a function

Cannot manually call signal handler `Keys.onDownPressed`

Compile and run the attached qml.

Press Down, note that "Down Pressed" is shown in console

Press Left, note that "Left Pressed" is shown in console, but "Down Pressed" is not shown. There is also the error message

qrc:/qt/qml/qt-onDownPressed/Main.qml:17: TypeError: Property 'onDownPressed' of object QQuickKeysAttached(0x55aceb6ac270) is not a function