I was looking at the pg in the above post, and noticed that the near plane is positioned incorrectly.
It seems that passing in a source plane to meshBuilder's createPlane function translates the plane in the wrong direction, and also rotates it so that it is facing the wrong way.
For a plane with normal (0,0,1), and a point on the plane (0,0,10), meshBuilder will position the plane at (0,0,-10) and face it looking along the -ve Z axis.
Example pg, with what I believe are fixes here.