IRB 14050 and "Arm-Angle Reference Direction" setting

I've been told that I should set Arm-Angle Reference Direction to Axis 1 in the controller configuration when using the YuMi Single Arm Robot. I've got a few questions:
  • if that is important (avoid singularities, etc.) why it is not the default when adding a controller From Layout?
  • how is that setting manged when programming online with the Flexpendant only?
  • where is such option (and its recommended value) documented? I couldn't find it on the robot Product Manual or RobotStudio Operating Manual.