Yes, the Wall Closure graphics is written in GDL for the Windows, but only in 2D, so its geometry is not generated in 3D, hence you do not see it in Section either. Theoretically, it could be scripted in 3D as well, but GRAPHISOFT chose not to do that.
You would have to use Lines and Fills, which you could save as a Patch object and place instances of that in your Sections.
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac28