Yes, I think it's by design. When you move your face left, it moves the same direction on the screen. It makes it easy to line up.
Compare this to a web cam. When you move your face left, it will actually move to the right (on the screen), which makes it hard to stay in the frame.
Everything you see in the screen is actually reversed (like I said, to make it easier to stay in frame). So when the picture is taken, it's "flipped" to appear how it would if someone was standing behind the camera.
I hope that makes sense. I know it sounds confusing!