[Bf-cycles] Cycles loads RGBA textures "premultiplied"?

[Jason Clarke]

I've noticed Cycles always loads RGBA textures with black in the transparent areas, as though the file was premultiplied. (Even if blender itself is loading the file with straight alpha). Why does it do this? Is there a way to disable it? It makes it impossible to store anything in a texture's alpha channel except actual transparency. Trying to store something like bump or roughness data in the alpha channel will ruin whatever is being stored in the RGB side.

-Jason (JtheNinja)