I am working on custom food meshes for The Sims 3 and I found that exporting through different pipelines produces different vertex counts.
Using the same mesh:
OBJ → Blender → MilkShape → WSO → TSRW
• AI-generated OBJ: 471 vertices / 482 triangles
• Blender: 243 vertices / 482 triangles
• After exporting as WSO in milkshape and creating a package in TSRW:
MOLD: 471 vertices / 482 triangles
The vertex count is preserved.

However, with:
OBJ → Blender → MilkShape → S3ACG → replace MOLD
When saving as s3asc in MilkShape, it shows: "509 vertices split". After replacing the MOLD, the result becomes:
• MOLD: 752 vertices / 482 triangles
The increased vertex count remains even if I import the MOLD back into Blender or TSRW.
I assume this is caused by different handling of TS3 render vertices, but I do not understand why WSO keeps 471 vertices while S3ASC creates additional splits.

The reason I would like to solve this is that the TSRW workflow is inconvenient for GeoStates. TSRW treats the exported package as a new object, so all internal resource indexes/TGIs are changed and I have to manually restore them. Also, creating different GeoState meshes can only be done inside TSRW, which makes the process complicated.
Using the S3ASC/MOLD method is much more convenient: I can create different GeoState meshes freely in Blender, calculate the required values, and write the GeoState data directly into the MOLD. It also keeps the original resource indexes intact.

Is there any way to prevent the "509 vertices split" during S3ASC export, or preserve the original vertex layout when using S3ASC? Any advice would be greatly appreciated.