Rhino after making a proper UV mapping and exporting the mesh as FBX or OBJ, create an extra set of UV mapping meshes. I mean instead of creating a unique UV mapping mesh it divided itself into little meshes as shown in the video.
In RizomUV importing the UV-mapping islands are not welded.
In the newer version of RizomUV (Vr 2022.1.103 or superior), there is the “magnet weld” feature. After loading, select all your islands then use that feature, it fixes the issue.
In RizomUV:
Select the “Edge Mode“. [F2]
Select all edges [Ctrl] + [A]
In Magnet-Weld put for example 0.1
Press “Magnet-Weld“
This will merge all islands in the same way as the original Rhino file