Terrain Details - Detail Mesh Scaling Issues...

I'm adding various rocks to my terrain but it looks like the built in randomization routines (height & width) are going negative and turning the rocks inside out. I would imagine that for grass textures this would be desirable as it would produce a mirror image of the bill-boarded texture. But for detail meshes it is a problem.

As you can see in the image above, the rock in the left foreground is inverted, but the one in the right background isn't? Am I doing something wrong here in the way I'm placing detail meshes -or- is this a bug within Unity 3D itself?