QSplitter does not honor preferred height

When adding the widget to QSplitter, it grabs more space than needed from child widgets, resizing them below preferred height (from sizeHint()), while adding more then preferred height to the new widget.

In the attached example QSplitter holds two widgets: W1: 335 px (preferred 200px) and W2: 220px (preferred 200px). Adding new widget W3 with preferred height of 100px changes the heights as follow. W1: 171px, W2: 112px, W3: 269px. So, even though there is enough space to give all widgets preferred size, QSplitter instead gives too much to the new widget, restricting the previous ones.

If this is intended behaviour, is it documented somewhere?