QColorDialog::ColorDialogOptions don't do what the docs say they do

The ShowAlphaChannel and DontUseNativeDialog options in QColorDialog do not behave as documented under Linux. Consider the following code snippet:

#include <QApplication>
#include <QColorDialog>
#include <QColor>

int main(int argc, char* argv[])
{
QApplication app(argc, argv);
QColorDialog::getColor(QColor(100, 100, 100), 0, "Test", QColorDialog::ShowAlphaChannel);
}

When I execute this code on linux (Fedora 13 64-bit), the alpha channel is not shown. If I add the QColorDialog::DontUseNativeDialog option to the above, I do get an alpha channel in my dialog, but the Qt documentation for DontUseNativeDialog says this option only affects Mac: "Use Qt's standard color dialog on the Mac instead of Apple's native color panel."

While I can understand that the native color dialog on my system might be erroneously implemented (probably a bug in KDE), the documentation for DontUseNativeDialog is misleading because in this case I seem to get a different dialog with it under Linux too, not just under Mac.