A full window QWidget does not stay minimized when it should

A minimal reproducer:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget *main = new QWidget;
    main->setWindowState(Qt::WindowFullScreen);
    main->show();

    return a.exec();
}

Upon launching, the window is shown in full screen, which is expected. Then press Win+D to minimize everything and show desktop. After that, fire up any other window (file explorer, browser, whatever other than Qt window), and the unexpected thing is that Qt window shows itself while it is not told to. It should stay minimized.