When translating a node, can I avoid copying the default value from the original language
Unset the field values in a hook_ENTITY_TYPE_translation_create:

use Drupal\node\NodeInterface;

/**
 * Implements hook_ENTITY_TYPE_translation_create().
 */
function mymodule_node_translation_create(Nodeinterface $translation) {
  if ($translation-&gt;getType() == 'product') {
    unset($translation-&gt;body);
  }
}