After I thought about it, I realized that maybe the issue the whole time was with the texture setRepeat setting. I did not need the setEdgeClamp setting to make it render correctly. I removed the workaround from Seb and set the mapper directly to the vtkXMLPolyDataReader output and it works correctly. The only recommendation I have is that the default value for vtkTexture repeat property is set to true so it matches the way standard VTK and Paraview operate. Should I close the issue in github or leave it open with the above recommendation?
Thanks to Seb for helping me through this.