It should be better documented that the file dialog opened on Linux is not necessarily native if the static functions are called

There seems to be implementation for the file dialog style for Linux in the qgtkstyle.cpp (for both Qt 4.8 and Qt 5), but even when testing with the 'standarddialogs' example and running it with the gtk style:
./standarddialogs -style gtk

the dialog shown is not purely native looking on Ubuntu 12.04 (Unity desktop).

From QFileDialog::getOpenFileName() (Qt 4.8) e.g.:
"On Windows, and Mac OS X, this static function will use the native file dialog and not a QFileDialog."

Qt 5.2 documentation states:
"The easiest way to create a QFileDialog is to use the static functions. On Windows, Mac OS X, KDE and GNOME, these static functions will call the native file dialog when possible.

fileName = QFileDialog::getOpenFileName(this,
tr("Open Image"), "/home/jana", tr("Image Files (*.png *.jpg *.bmp)"));"

If it really shows the native dialog in some occasions, could the "when possible" be elaborated a bit more thoroughly?

Note! It is not very clearly stated in the QFileDialog documentation as a whole that you need to use the static functions e.g. getOpenFileName() show the native file dialog. And the non-static ones shows Qt's QFileDialog widget. Is it possible to rephrase this sentence to make it more clear: "The easiest way to create a QFileDialog is to use the static functions. On Windows, Mac OS X, KDE and GNOME, these static functions will call the native file dialog when possible."