Named rescore queries

Named queries help me to identify which part of the query hit. For normal queries this works perfectly. However for rescore queries named queries don't show up in the response.

Question: Is this a bug or intentional? Is there a workaround?

Update: I raised a feature request

I attached some code to reproduce the problem:

Set up a test index with a single document

PUT /test
{
  "mappings": {
    "properties": {
      "field1": {
        "type": "keyword"
      },
      "field2": {
        "type": "keyword"
      }
    }
  }
}

POST /test/_doc/1
{
  "field1": "a",
  "field2": "b"
}

"Normal" and rescore query.

GET /test/_search
{
  "query": {
    "term": {
      "field1": {
        "value": "a",
        "_name": "query_field_1"
      }
    }
  },
  "rescore": {
    "query": {
      "rescore_query": {
        "term": {
          "field2": {
            "value": "b",
            "_name": "query_field_2"
          }
        }
      }
    },
    "window_size": 50
  }
}

Response: Only the name of the "normal" query shows up in matched_queries. That "query_field_2" must have also hit can be ensured by comparing the score with and without the rescore query.

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 0.5753642,
    "hits" : [
      {
        "_index" : "test",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 0.5753642,
        "_source" : {
          "field1" : "a",
          "field2" : "b"
        },
        "matched_queries" : [
          "query_field_1"  <<-----HERE I'D EXPECT query_field_2------
        ]
      }
    ]
  }
}