When using generated noise textures (i.e. "Noise", "Magic", "Voronoi", ...) for the displacement modifier or as surface for a cube there are no seams visible.
See my gif for ants for demonstration (Cube with Voronoi Texture):
How does blender achieve this? Does it sample the noise texture on a sphere and projects it onto the object like proposed here (https://gamedev.stackexchange.com/questions/97591/how-to-create-a-seamless-cubemap-noise-texture)?
Edit: Thank you @moonboots and @crantisz - now i got it :) The word texture was always connected with 2D in my brain and did not match with 3D at first ;) So in other words: The space itself around the object is filled with a 3D - Voronoi field / pattern (see example one below) and you can see the intersection between the object boundary with this 3D pattern on the objects surface.