How to use with simple shapes?

[chickenSandwich]

I am wondering if I am misunderstanding how to use this module. I am testing with the simple shapes in trimesh, but am not able to produce something that makes sense. Here is a demonstration:

import trimesh
import xatlas
from PIL import Image

# mesh = trimesh.creation.box()
# mesh = trimesh.creation.icosphere()
# mesh = trimesh.creation.uv_sphere()
# mesh = trimesh.creation.cylinder(radius=1, height=1)
mesh = trimesh.creation.capsule(radius=1, height=1)
atlas = xatlas.Atlas()

atlas.add_mesh(mesh.vertices, mesh.faces)

chart_options = xatlas.ChartOptions()
chart_options.fix_winding = True

pack_options = xatlas.PackOptions()
pack_options.blockAlign = True
pack_options.create_image = True
pack_options.bruteForce = False
pack_options.resolution = 0
pack_options.texels_per_unit = 0
atlas.generate(pack_options=pack_options, chart_options=chart_options)

img = Image.fromarray(atlas.chart_image)
# img.show()
# img.save("box.png")
# img.save("icosphere.png")
# img.save("uvsphere.png")
img.save("capsule.png")

vmapping, indices, uvs = atlas[0]
# print(atlas[0])

u = trimesh.Trimesh(vertices=mesh.vertices[vmapping], faces=indices, visual=trimesh.visual.texture.TextureVisuals(uv=uvs, image=img), process=True)
u.show()

I have tried with these different simple meshes, and I'm expecting the resulting mesh to show a well-wrapped mesh, but with no luck. If I change the pack_options.bruteForce=True for the trimesh.creation.box it makes the most sense, but to be honest I was thinking that the produced unwrapped image would be closer to a cube mapping.
I also tried exporting the .obj and manually adding an .mtl, but that produces the same results.

Can anyone lend a hand?
Am I misusing this tool?
Is there an error in my script?

Thank-you.