Quote - just so we're clear - here's the cylinders with checkered maps applied.

I do understand what you are saying.  The best way for me to communicate to you what I am saying is represented below:

1) Here is a cylinder with a horrible UVMap.  However, that UVMap was first created using a Planar projection.  It is rendered in poser with the default texture-checker mapped to it.

Here is the UVMap for that cylinder:

Here is the cylinder in Hexagon and I have selected one of the top faces so it is highlighted in the terribly done UVMap.

And, when you remove the texture to better see if there is any artifact present, this is what you get in Poser.

There is NO artifact present even with a horribly distorted UVMap in a Planar Projection.  If you apply another texture image just in case you may think it is due to the absence of any texture, this is what you get:

(Concrete texture image mapped using that very bad UVMap)

There is no artifact present no matter how bad the UVMap is with a Planar projection from any axis.  Texture or no texture, the artifact is absent.  Other Projections vary in whether or not they will present an artifact on this object with Box Projections being the worst culprits and Cylinder and Spherical Projections only having one appropriate axis.

A UVMap is supposed to be used primarily for applying 2D images to 3D surfaces.  Using procedural textures, generated by the computer, doesn't need a well done UVMap.  The computer does not care about whether or not the information is understandable in two dimensions.  For the purposes of texture mapping an image, we DO care and must have a 2D representation of a 3D surface in order to be accurate.  That is WHY there are UVMaps.

They're not supposed to act this way and influence this type of artifact.  That's what I'm getting at.  It doesn't matter one bit regarding the quality of the UVMaps or their vertice locations on the included experimental objects in that collection or whether those maps are suitable for appropriately applying 2D images to a 3D surface with accuracy.