Views does not add reverse relationship data for entity_reference fields not defined in configuration

Attaching some possibly related issues.

I'm working on a module which provides several entity types with entity reference baseFields between them, both single- and multi-value ones. Here's how I got around this problem.

/**
 * Implements hook_views_data_alter().
 */
function mymodule_views_data_alter(array &$data) {
  // Entity reference base fields should have a reverse relationship in Views
  // (just like the sitebuilder-added entity reference fields have), not only
  // a forward relationship.
  // @see core_field_views_data()
  $entity_type_manager = \Drupal::entityTypeManager();
  /** @var \Drupal\Core\Entity\EntityFieldManager $entity_field_manager */
  $entity_field_manager = \Drupal::service('entity_field.manager');
  $entity_types = $entity_type_manager->getDefinitions();
  foreach ($entity_types as $source_entity_type_id => $source_entity_type) {
    // Handle only our own entity types as source.
    if ($source_entity_type->getProvider() != 'mymodule') {
      continue;
    }
    // Handle only content entity types as source.
    if (!($source_entity_type instanceof \Drupal\Core\Entity\ContentEntityType)) {
      continue;
    }
    $base_field_definitions = $entity_field_manager->getBaseFieldDefinitions($source_entity_type_id);
    foreach ($base_field_definitions as $base_field_id => $base_field_definition) {
      // Handle only entity reference fields.
      if ($base_field_definition->getType() != 'entity_reference') {
        continue;
      }
      /** @var \Drupal\Core\Field\TypedData\FieldItemDataDefinition $item_definition */
      $item_definition = $base_field_definition->getItemDefinition();
      $field_definition = $item_definition->getFieldDefinition();
      $field_storage = $field_definition->getFieldStorageDefinition();
      $target_entity_type_id = $field_storage->getSetting('target_type');
      $target_entity_type = $entity_type_manager->getDefinition($target_entity_type_id);
      // Handle only our own entity types as target.
      if ($target_entity_type->getProvider() != 'mymodule') {
        continue;
      }
      // Handle only content entity types as target.
      if (!($target_entity_type instanceof \Drupal\Core\Entity\ContentEntityType)) {
        continue;
      }

      // Here comes the heart of the dance.
      $pseudo_field_name = 'reverse__' . $source_entity_type_id . '__' . $base_field_id;
      $args = [
        '@label' => $target_entity_type->getLabel(),
        '@field_name' => $base_field_definition->getName(),
        '@entity' => $source_entity_type->getLabel(),
      ];
      // The sitebuilder-added entity reference fields have the same storage
      // schema regardless their cardinality. Sadly, this is not true for entity
      // reference base fields: multi-value fields (ones with cardinality != 1)
      // have a link table between the source and the target entities (just like
      // sitebuilder-added fields have one regardless their cardinality).
      if ($base_field_definition->isMultiple()) {
        $views_table = $target_entity_type->getDataTable();
        $field_table = $source_entity_type_id . '__' . $base_field_id;
        $field_field = $base_field_id . '_' . $base_field_definition->getMainPropertyName();
        $data[$views_table][$pseudo_field_name]['relationship'] = [
          'title' => t('@entity using @field_name', $args),
          'label' => t('Rev: @entity', $args),
          'group' => $target_entity_type->getLabel(),
          'help' => t('Relate each @entity with the @field_name field set to the @label.', $args),
          'id' => 'entity_reverse',
          'base' => $source_entity_type->getDataTable(),
//          'entity_type' => $source_entity_type_id,
          'base field' => $source_entity_type->getKey('id'),
//          'base field' => 'entity_id',
          'field_name' => $source_entity_type_id . '_' . $base_field_id,
          'field table' => $field_table,
          'field field' => $field_field,
          'join_extra' => [
            [
              'field' => 'deleted',
              'value' => 0,
              'numeric' => TRUE,
            ],
          ],
        ];
      }
      else {
        $field_table = $target_entity_type->getDataTable();
        $field_field = $base_field_id;
        // Cannot use the `entity_reverse` @ViewsRelationship handler plugin here,
        // since it always creates two JOINS, which is totally unneeded for
        // single-value baseFields, because their value is available right away on
        // the entity_type_field_data table.
        $data[$field_table][$pseudo_field_name]['relationship'] = [
          'title' => t('@entity using @field_name', $args),
          'label' => t('Rev: @entity', $args),
          'group' => $target_entity_type->getLabel(),
          'help' => t('Relate each @entity with the @field_name field set to the @label.', $args),
          'id' => 'standard',
          'base' => $source_entity_type->getDataTable() ?: $source_entity_type->getBaseTable(),
          'entity type' => $target_entity_type_id,
          'base field' => $base_field_id,
          'relationship field' => $target_entity_type->getKey('id'),
        ];
      }
    }
  }
}

I know it's somewhat quick and dirty, but hopefully helps moving forward.