Exporting static mesh, then importing that fbx(w/ Import Normals and Tangents) doubles vertex count

Static meshes exported from the engine have more vertices when imported back into the engine.

Occurs on?
4.13 - 3172292 - YES
4.16 - 3466753 - YES
4.17 - CL3512142 - YES

1. Import the attached sphere
2. Open the static mesh asset (Vertex count is 560)
3. Right Click the asset in the ContentBrowser>Asset Actions>Export (Create a unique fbx)
4. Import the unique FBX with Normal Import Method set to "Import Normals and Tangents"
5. Open the static mesh asset

Result: Vertex count is 1560
Expected: Vertex count is the same as step 2 (560)