If I am correct you are looking at these object in a Section View or Interior Elevation View in which you see them from the side.
In that case the curved parts of the outline of the object is not visible. It is like it is not there.
This is actually a shortcoming of GDL and those Library Object have been like this for as long as I know the program.
Usually there are 2D side views of such objects in the Library to be used in such cases.
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