As evidenced here:

public Entry<org.opendaylight.yangtools.yang.data.api.InstanceIdentifier, NormalizedNode<?, ?>> toNormalizedNode(
final Entry<org.opendaylight.yangtools.yang.binding.InstanceIdentifier<? extends DataObject>, DataObject> binding) {
Entry<org.opendaylight.yangtools.yang.data.api.InstanceIdentifier, CompositeNode> legacyEntry = bindingToLegacy
.toDataDom(binding);
Entry<org.opendaylight.yangtools.yang.data.api.InstanceIdentifier, NormalizedNode<?, ?>> normalizedEntry = legacyToNormalized
.toNormalized(legacyEntry);
LOG.trace("Serialization of {}, Legacy Representation: {}, Normalized Representation: {}", binding,
legacyEntry, normalizedEntry);
if (isAugmentation(binding.getKey().getTargetType())) {

the translation uses intermediate representation in CompositeNode, since this is performance-critical path, this has to be avoided.