Interesting. I understand what you mean by the back piece with the extra layer but the front Im not sure.
There is one extra piece facing out that just covers the center portion and goes under the hidden pockets but ends about half way in? If so that makes sense since it would look nice in the middle but it adds no extra bulk to the edges. Next wallet I make with goat on the outer Im going to try one layer like that, I don't know why but I thought it would be too thin on its own without some type of liner. Im assuming the liner you used is more for aesthetics, its not heavy enough to add any bulk.
Either way awesome colors. What edge paint is that and what color?