Ambient gradient difference from Unity standard shader

Hi! I'm trying to make a shader that behaves the same as the new standard shader in unity 5 so that I can then extend it. I used the "Lit (PBR)" preset, but ran in to a problem with the Ambient gradient. It seems the SF shader applies the ambient gradient a bit differently. Maybe you are already aware of this but I wanted to ask about it at least.

The left sphere is the shader forge one and the right uses the standard shader. Metallic/gloss etc. all set to 0.