Converting a mesh to Nanite merges mesh sections with the same material index, but with different material overrides

When a mesh with multiple sections which point to the same MaterialIndex but have different settings enabled (e.g. bCastShadow is enabled on only one section) is converted to Nanite, the material slots are collapsed (even though they have different settings applied).

Enabling Nanite on this mesh collapses these slots even though they contain different settings and it doesn't seem possible to create multiple sections with the same material slot name on a Nanite mesh, one is always removed when the mesh builds.

• Create a non-Nanite mesh with two sections and two material slots
• In the static mesh editor, point both sections at the same material slot and remove the unused material slot. This works as expected for non-Nanite meshes and you can toggle for example shadow casting on a single section so that only one cube casts a shadow, but both use the same single material slot
• Enabling Nanite on this mesh and applying the change, collapses these slots even though they contain different settings