Section of strut displays a much smoother texture.

The strut on top of the cube was duplicated, then resized to the current shape.
After resizing, the insulation texture was applied, but had 2 smooth triangles extending from the top to the bottom. I then cycled through the part smoothing options to try remove the smoother triangles, after which the two smooth triangles became a large rectangular smooth patch, as seen in the image. No further changes were observed when cycling through the smoothing options again.