Because the original Skeletal Mesh is used to define the proportions of the Skeleton asset, any other Skeletal Meshes using that Skeleton asset that have different proportions (such as a mesh that is much shorter than the original one) will require retargeting to work properly. Without it, the Skeletal Meshes of varied proportions would try to use the translation data of the original mesh, leading to the types of errors seen at the beginning of this document.