The 'View Drainage as Solids' command was not intended to display the structures as 3D elements with thickness showing an inner diameter as a hole. It was designed to have a way to display a solid shape in a 3D design to aide in clash detection and help visualize clearance issues. It doesn't create a 3D shape with the thickness or any structure property, just a solid cylinder or box for pipes and solid shapes for other structure types.
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communities.bentley.com/.../260229