diff -u b/core/modules/field_ui/src/Form/FieldStorageAddForm.php b/core/modules/field_ui/src/Form/FieldStorageAddForm.php
--- b/core/modules/field_ui/src/Form/FieldStorageAddForm.php
+++ b/core/modules/field_ui/src/Form/FieldStorageAddForm.php
@@ -574,8 +574,6 @@
    *
    * @param string $field_name
    *   The machine name of the field.
-   * @param string $existing_bundle
-   *   (optional) The name of the existing bundle (not $this->bundle).
    *
    * @return array
    *   An array of settings with keys 'field_config', 'entity_form_display', and
@@ -586,30 +584,18 @@
    * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
    * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
    */
-  protected function getExistingFieldDefaults(string $field_name, string $existing_bundle = ''): array {
+  protected function getExistingFieldDefaults(string $field_name): array {
     $default_options = [];
     $field_map = $this->entityFieldManager->getFieldMap();
-    if ($existing_bundle) {
-      // Validate that $existing_bundle is different from $this->bundle and that
-      // the field is defined for the supplied bundle.
-      if ($existing_bundle === $this->bundle) {
-        return [];
-      }
-      if (empty($field_map[$this->entityTypeId][$field_name]['bundles'][$existing_bundle])) {
-        return [];
-      }
-    }
-    else {
-      // If $existing_bundle is not supplied, then find a suitable candidate.
-      if (empty($field_map[$this->entityTypeId][$field_name]['bundles'])) {
-        return [];
-      }
-      $bundles = $field_map[$this->entityTypeId][$field_name]['bundles'];
-
-      // Sort bundles to ensure deterministic behavior.
-      sort($bundles);
-      $existing_bundle = reset($bundles);
+
+    if (empty($field_map[$this->entityTypeId][$field_name]['bundles'])) {
+      return [];
     }
+    $bundles = $field_map[$this->entityTypeId][$field_name]['bundles'];
+
+    // Sort bundles to ensure deterministic behavior.
+    sort($bundles);
+    $existing_bundle = reset($bundles);
 
     // Copy field configuration.
     $existing_field = $this->entityFieldManager