NavMeshComponents | High Level API Components for Runtime NavMesh Building | Game Engine library

Problem:
I'm having problems baking a C# generated mesh using the NavMeshSurface script provided in NavMeshComponents.

If I bake the NavMeshSurface on the "WalkableMesh" GameObject the baking is over quickly and nothing is walkable. The NavMeshSurface does not turn blue to indicate it is navigable.

Setup/Installation:
Here is a complete zip of the assets if you would like to see the behavior I describe below. Copy these into your project root (I'm using Unity 2019.3) and you'll be half way there.

Below are the settings for my agent. You will have to set your agent to these settings in the Navigation window. To modify these settings, in the toolbar select Window->AI->Navigation

These are the settings you'll have to set on the PLANE NavMeshSurface. This allows the NavMesh geometry to be detailed enough to bake single tiles at the 32x16px size.

Further Information:
I'm creating the meshes I'm trying to bake by iterating over a TileMap. This allows me to have separate areas with completely separate meshes for the differing pathing costs. As I said above baking does not work on these meshes directly.

I can bake the NavMesh INDIRECTLY by taking a separate plane and baking that plane ANYWHERE in the scene. Baking will bake both the plane and the NavMeshSurface on the "WalkableSurface" GameObject. The area assigned to the generated NavMesh is determined by the plane GameObject's NavMeshSurface area settings.

1) Why does the WalkableMesh object not bake without this plane?
2) Why does the plane bake the WalkableMesh?

You can see the square plane baking the WalkableSurface below.

The NavMeshSurface I'm adding in code also reports the Namespace could not be found but it is added nonetheless.
Error CS0246 The type or namespace name 'NavMeshSurface' could not be found (are you missing a using directive or an assembly reference?)