Wish to improve IfcCurtainWall description

1) Second sentence says "Curtain wall is represented as a building element assembly", suggested to change "may be represented as an assembly or single instance"

2) Needs clarification what entities can be used for curtain wall parts in case of assembly.
(I did not found nothing better IfcBuildingElementPart but my user request more specific for panels and mullions, not sure what can I do)