Workbench, pointiness and dirt masks

I came across a problem with using pointiness in shader setups and with using dirt maps in vertex color.

Let’s take a simple element like this:

Solid looks good.

Same for carpaint

But using pointiness node (Cycles) inside a shader gives:

Vertex color dirt mask also have artifacts, but different kind. Second screencap is with cranked contrast.

Is this by design and/or should this work that way? Or maybe this should be considered a bug?
How to properly do modeling when you want to use pointiness or dirt masks down in the pipeline?