The ‘orientation axis’ only makes a difference if the beam is inclined. In an inclined beam, an ‘aligned’ load orientation would interpret the inputs as exactly perpendicular to the beam. In contrast, a ‘gravity’ load orientation would interpret the inputs as being along the global Y-axis (useful, for example, because gravity always acts along the global Y-axis regardless of how the beam is oriented, but wind almost always acts perpendicular to the beam).