A skilled GDL scripter is capable of producing amazingly clean objects, but the catalog of clean GDL objects is not as deep as one would like it to be. (See the sidebar links here in bd-MAP for access to some of the GDL catalog.)
So we rely on third-party catalogs from time to time, but the objects are often polygon nightmares. AC 16 has a new tool and a new way to clean them up.
Clean is good.