Called on demand from systems that need to fully update an AssetData's tags. When an Asset is loaded its tags are updated by callingUObject::GetAssetRegistryTags, but GetAssetRegistryTagsExtended is not called, and tags that exist in the Old AssetData but not in the results from GetAssetRegistryTags are kept because they might be extended tags. When an asset is saved, GetAssetRegistryTagsExtended is called and all old tags are deleted in favor of the new list. AssetFullyUpdated allows a manual trigger of the on-SavePackage behavior: GetAssetRegistryTagsExtended is called and all old tags are deleted in favor of the new list.