https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifcindexedtexturemap.htm
Here it states:
" Subtypes of IfcIndexedTextureMap establish the index attribute corresponding to subtypes of IfcTessellatedFaceSet defining the corresponding index lists of vertices."
So, if I want textures on my IfcTriangulatedFaceSet, I will of course use the subtype IfcIndexedTriangleTextureMap. But if I want to have textures on my IfcPolygonalFaceSet, there seems to be missing a corresponding IfcIndexedPolygonalTextureMap.
The IfcIndexedTextureMap is abstract, so we can’t use that.