Per Instance Random node not working in material layer

Licensees report that the definition of the USES_PER_INSTANCE_RANDOM macro only considers it in the context of the base material. 
As a result Per Instance Random used only in material layers does not work.

1. Create a material (M_Base) using the Material Attribute Layers node.
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2. Create a material layer (ML_Layer) with a Per Instance Random node connected to BaseColor
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3. Create a material instance (MI_Inst) with M_Base as the parent and set ML_Layer to the Background layer
4. Place the Cube with the Foliage tool and assign MI_Inst to the material slot
   Play that Level. All Cubes are rendered in black.
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   It seems that random numbers on the material layer side work by creating a dummy Per Instance Random node in the base material. [Image Removed]