DockWidgets cannot be detached from window

I have a simple window with a QQuickView as the central widget and a few DockWidgets attached along the left side. It is impossible to drag the dock widgets away from the window to detach them on Mac OS. I did not test on Windows.

I've included a trivial project demonstrating the issue. Download. Qmake. make. Open the app. Try to drag the top left dock widget (named "ONE") away from the window. Fails in an obvious way.