Custom Node interprets MaterialAttributes inputs as float3

It seems that the Material Editor's Custom nodes don't handle inputs of type FMaterialAttributes correctly, and instead interpret them as float3.

1. Create a material like this, where a MaterialAttributes struct is used as the input to a Custom node:
   [Image Removed]
2. Observe shader compilation errors and/or generated HLSL code indicating that the MaterialAttributes input is interpreted as being of type float3