Incorrect default blend equation

Observed behaviour:
When render capturing a scene that contains an entity with QDiffuseSpecularMaterial with enabled alpha blending, the capture result looks different from the screen.
I changed the sphere material in rendercapture-cpp example to QDiffuseSpecularMaterial.
See my screenshot:
RenderCapture_transparentSphere.png
the modified main.cpp and the saved capture result capture.bmp attached.

Additional information:

I tried to reproduce it on another environment. The incorrect behaviour is observable only if the backbuffer format uses the alpha channel (i.e. RGBA).

Possible culprit:
The defaults of QBlendEquationArguments for the alpha component are source alpha = 1 and dest alpha = 0. This is different from the generally suggested values source alpha = 0 and dest alpha = 1 which is described at https://doc.qt.io/qt-5/qt3drender-protips.html .