@rom

Looks again like a vertex normal data problem on your side. That's the .FBX provided directly rendered in Houdini.
I know Max have hundred of options in the .FBX import dialog, there must be something about recomputing vertex normal's, or creating Smoothing Groups that need to be disabled.
The goal is the read vertex normals MoI's created.

Previously you said : `MOI's export preview is rather schematic and hides the bare truth`.

Actually that's not true, the mesh MoI display at export time should look exactly the same in your DCC viewport. If you see a difference, like dark shading area or ugly sharp triangle like you post above using the 'generic' display mode (opengl/directx/Vulkan), it's a good indication that something is lost in the import process, or something get mess-up after the import (vertex merging, attempt to reduce/edit the geometry, normals re-computing using an average method etc).