Thank you for being patient.
I would like to share with you that the point raised by you is not really an issue, but the explanation for this behavior is the different interpretations of 3D rotation properties in ECMA-376 standard and PowerPoint. The chart.xml ‘rotX’ item is interpreted as ‘Y rotation’ and ‘rotY’ - as ‘X rotation’ option in PowerPoint UI (see explanation.jpg).
Moreover, the description of these properties is as under,
Chart.Rotation3D.RotationX property returns or sets the rotation degree around the X-axis, i.e. in the Y direction for 3D charts (between -90 and 90 degrees). The property matches with the 220.127.116.11 rotX (X Rotation) item in ECMA-376 and with the “Y Rotation” option in PowerPoint 2007+
Chart.Rotation3D.RotationY property returns or sets the rotation degree around the Y-axis, i.e. in the X direction for 3D charts (between 0 and 360 degrees). The property matches with the 18.104.22.168 rotY (Y Rotation) item in ECMA-376 and with the “X Rotation” option in PowerPoint 2007+.
I hope this will clarify the concept. Please share if I may help you further in this regard.