Always the same! :)
Export to Affinity V1 for have only separated closed curves (or surfaces ) for any 2D design!
seems Aff V2 resolves now from no closed curves...(as shown on my previous video)
https://moiscript.weebly.com/uploads/3/9/3/8/3938813/fullsizerender.mov

It's legitim to have from any 3D view of a mechanical piece from a 3D prog only faces visible for any graphic post production...

In fact a sort of internal Contour Silhouette for each surface...