There are two or three things here that are worth mentioning:
When you apply an image on a face and apply the same image on its reverse, the latter one is always flipped (or mirrored). This is particularly useful and essential when you apply semi transparent images to create 2D plants for instance. Without this feature you'd always keep manually flipping them all the time
a simple face drawn on the xy plane shows its reverse face upwards because SU presumes that that's going to be the bottom of any structure you are going to build on top (above the ground level). And unless you use the PP tool, it's correctly oriented since it will be facing inside. In fact, the PP tool is the "exception" because when you start to use it, it flickers a little bit until "realises" that you are going to push/pull that face up and immediately - very smartly - decides to leavi it like that (the flickering actually being the new face and the old one z fighting a bit).
Orient faces work best when there is just a simple volume surrounded by the faces (i.e. no wall thickness, no faces that may face either this way or the other etc.). Once you have several volumes combined together, SU may not be able to decide what is outside and what is not. Try a simple test:
Draw a rectangle
PP it up to a certain hight
now Ctrl+PP it up to another height (leaving a face in between). This face is a single face and how SU should be able to decide that when orienting faces, where it should orient? Click on any of the outside faces and choose orient faces. You'll see the screwed up result.
