Cap and exclusion doesnt work

I am trying to cap the surface to exclude all geometries out side the cutting shape. somehow the cap doesnt work in Grasshopper but if I bake the geometry in rhino it somehow does.

Split_Srf_Exclude (272.8 KB)

Your surface is not closed at the seam…and you’ll need pufferfish plugin to make it work.

Split_Srf_Exclude (277.6 KB)

Split_Srf_Exclude (279.4 KB)