API: Chaining EntityTag.delete does not work

Have a look at this API call:

$result = civicrm_api3('EntityTag', 'get', array(
'sequential' => 1,
'return' => array("id", "entity_id"),
'options' => array('limit' => 1),
'api.EntityTag.delete' => array('id' => "\$value.id", 'entity_id' => "\$value.entity_id"),
));

This should get one EntityTag (limit 1), and delete it using a chained API call. (I explicitely mention entity_id, because this is required since c683526)

Here is the result I get:

{

"is_error": 0,
"version": 3,
"count": 1,
"id": 3096,
"values": [
{
"id": "3096",
"entity_id": "1",
"api.EntityTag.delete":

{ "is_error": 1, "not_removed": 2, "removed": 0, "total_count": 2, "error_message": "Unable to remove tags" }

}
]
}

So 'api.EntityTag.delete' says 'not_removed':2, although I requested to remove only one EntityTag. I reproduced this as user 1 in the API explorer, so it is not a permission issue.