So in the rules it gives examples on how to change large and massive character facing. However, I did not see anywhere that facing actually matters. The rules say they can draw line of sight from any corner they are occupying so I assume they can shoot backwards. Likewise they cannot move diagonal but I do not see anything to prevent them from moving sideways or backwards. So why change facing? Am I wrong in my interpertation? Thanks!

They can't squeeze into spaces that are smaller than their dimensions. There are times when they will have to reface in order to get through certain areas of the map.

Good point. That was the one exception I thought of. So are my line of sight and movement interpretations correct?

Good point. That was the one exception I thought of. So are my line of sight and movement interpretations correct?

Yes

Facing only maters with non-square units (ie e-web). As you can't move diagonal, sometimes you have to spend a movement to rotate yourself.