[ProBuilder] Material will not propagate to new faces after several boolean subtractions

UPDATE: It has been noted that Boolean operations are an experimental feature and should not be treated as a blocker for any release purposes.

When working in ProBuilder and using several boolean subtractions on a shape, the material applied to the shape will fail to propagate to the new faces created (See attached capture).

Steps to reproduce:
- Launch Unity with a new 2019.3 project, installing the ProBuilder package via Package Manager (on staging at this time, alternatively you can download the attached project)
- In any scene, create a new ProBuilder shape (cube ideally)
- Create another ProBuilder shape (cube ideally) which is smaller
- Position the smaller ProBuilder shape inside of the initial shape and select both objects
- Menu: Tools> ProBuilder > Experimental > Boolean (CSG) Tool
- Ensure the first larger mesh has been properly allocated to the first (left) pane and the smaller to the second (right) pane
- Set the “Operation” to “Subtraction”
- Apply the operation
- Repeat these steps on the initial object/shape, nesting these subtractions inside
- Observe that after several subtractions (typically 2), the material of the parent shape is no longer applied to the new faces created
- (Optionally) If another, non-subtraction, operation which clones the object, is now done on this object/shape, observe that the materials on the cloned/object shape's faces will be corrected.