Because you need two of them together. Actually, you could just do it with pose dots to match the two but you would have to match tme every step, where a base conformer on top of/under a normal figure would simply move with and thus work with walk designer and so on quite easily. I.e. you have one figure with one texture and trans and another with the other texture and trans in the exact same pose and position. so that you can layer the materials. Effectively it works just like the 3-d version except that the 'layers' take place in three dimensions and are a UVmap on a figure.