Mesh from attached USD fails to import

UDN customer reported this issue:

Using legacy USDImporter, the attached USD throws these ensures

ensure(Primvar.Get(&UVs, Options.TimeCode));
ensure(Primvar.GetIndices(&Indices, Options.TimeCode) || !Primvar.IsIndexed());

and fail to import.

The file imports with Interchange although in 5.5 it is imported as skeletal assets. In 5.6, it is imported as a static mesh.

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