Why are entities still queried based on hook_schema()?

WOWZA. Worse:

The entity base table SQL columns are keyed by numeric indexes:

  ["schema_fields_sql"]=> array(

    ["base_table"]=> array(
      [0]=> string(3) "uid"
      [1]=> string(4) "uuid"
      [2]=> string(4) "name"
      [3]=> string(8) "langcode"
...

...which leaves me with this fancy hack:

  public function __construct($entity_type) {
    parent::__construct($entity_type);

    $columns = &$this->entityInfo['schema_fields_sql']['base_table'];
    $columns = array_combine($columns, $columns);
    unset($columns['uuid']);
    unset($columns['langcode']);
    unset($columns['signature']);
    unset($columns['signature_format']);
    unset($columns['preferred_langcode']);
    unset($columns['preferred_admin_langcode']);
  }

FWIW, further investigation showed that the corresponding EntityStorageController::save() operations are still using drupal_write_record(). drupal_write_record() completely relies on hook_schema().

So the current code is actually inconsistent on two fronts:

1) load() / buildQuery() uses the prepared SQL schema information, as prepared in entity info.

2) save() uses the literal information from hook_schema().

At minimum, only one of both, plz. ;-)

Related: #1774104: Replace all trivial drupal_write_record() calls with db_merge()