The root cause was that the bAllowCPUAccess property of the StaticMesh was not set to true. This property is essential for runtime access to the mesh data, which I overlooked.
The solution was straightforward once the issue was identified. I navigated to the problematic StaticMesh assets in the Unreal Editor and ensured that their bAllowCPUAccess flag was set to true under the mesh properties. This change allowed the CopyMeshFromStaticMesh function to execute successfully in the packaged game.