QWidget-gestures do not work

Run the Gesture examples from,

qt5/qtbase/examples/widgets/gestures/imagegestures

Try pinch, swipe and pan. They dont work.
Modify example to add tap and tapandhold gestures,

grabGesture(Qt::TapGesture);
grabGesture(Qt::TapAndHoldGesture);

Tap and TapAndHold gestures works.

Modify example to add, nativewindows attribute,

app.setAttribute(Qt::AA_NativeWindows);

Now 2 finger pan and 2 finger rotate works, and weirdly these gestures are treated as Pinch gestures.