Odd Refraction on Close Planes

We're seeing odd refraction when we have two close planes where the front plane has a translucent shader with a refraction not equal to one. I've included a project with the following setup:

• Two equally sized planes set one centimeter apart.
• The back plane has DefaultMaterial applied.
• The front plane has a very simple translucent shader with the index of refraction set to 1.1.
• A partially occluded sphere in the background.
  As you can see from the included screenshot, the back surface is refracted way more than seemingly possible given its proximity. Is this an issue with the material I've created or is this a bug in the lighting?

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1. Download the attached repro project
2. Set “Plane” to use the /Game/M_Glass_Clear and observe the refraction issue