Expected behavior of Qt::Tool style?

[Valistar]

Hello,

I'm looking at an application bug where on Windows, opening a dialogue causes the program to disappear from the alt-tab menu (though not the taskbar). This seems to be a result of the Qt::Tool flag + WS_EX_TOOLWINDOW style being applied to the dialog widget.
The widget hierarchy is QMainWindow->QDialog. Is it expected that applying this flag to a child seems to effect the parent, as far as how Windows handles it? I'd assume this would just prevent this dialog window from showing up in these places. Or am I missing something, or is something tragically wrong with the code/app somewhere?

I tried changing the hierarchy to QMainWindow->QWidget(central widget)->QDialog, with no effect. Making the QDialog a sibling, or removing the Qt::Tool flag does fix the alt-tab issue but is undesirable behavior.

Seemingly relevant snippets:

MainWin::MainWin(QWidget *parent)
    : QMainWindow(parent)
{
    ui.setupUi(this);
    ...
}
 
void MainWin::doClick()
{
 
    QScopedPointer<Poppy> theBox(new Poppy(this));
    theBox->setModal(true);
    theBox->setWindowState(Qt::WindowActive);
    theBox->exec();
}
 
Poppy::Poppy(QWidget *parent)
    : QDialog(parent)
{
    ui.setupUi(this);
    this->setWindowFlags(Qt::Tool); 
    this->setModal(true);
    ui.validationWarning->hide();
    // connect slots to signals
    ...
}

MainWin::MainWin(QWidget *parent)
    : QMainWindow(parent)
{
    ui.setupUi(this);
    ...
}

void MainWin::doClick()
{

    QScopedPointer<Poppy> theBox(new Poppy(this));
    theBox->setModal(true);
    theBox->setWindowState(Qt::WindowActive);
    theBox->exec();
}

Poppy::Poppy(QWidget *parent)
    : QDialog(parent)
{
    ui.setupUi(this);
    this->setWindowFlags(Qt::Tool); 
    this->setModal(true);
    ui.validationWarning->hide();
    // connect slots to signals
    ...
}

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