QdockWidget:: toggleViewAction(), dockwidget’s visibility is toggled on triggered() signal whereas it could/should be toggled() signal as user wants to control the dock visibility with some property, say checked.
If you set action.setChecked(true) or action.toggle(), it does not make any impact on dock’s visibility. Like in qdockWidget.cpp, line no. 679, we have

  QObject::connect(toggleViewAction, SIGNAL(triggered(bool)), q, SLOT(_q_toggleView(bool)));

Like if you try,

    b = w1->toggleViewAction();
    qDebug()<< b->isChecked();  // false, which seems incorrect
    // Following code does not make any difference as toggle does not emit triggered signal
    b->setChecked(false); 
    b->toggle();