Elasticsearch query with wildcard not working with icu_collation filter

icu_test.sh

#!/bin/bash

echo "==== Creating index ===="
curl -XPUT 'http://localhost:9200/icu_wildcard/?pretty=1' -d '{
    "settings" : {
        "index" : {
            "number_of_shards" : 1,
            "number_of_replicas" : 1
        },
        "analysis" : {
          "analyzer":{
            "unicode_l1": {
              "char_filter": [
                "icu_normalizer_nfc"
              ],
              "tokenizer": "icu_tokenizer",
              "filter": [
                "icu_collation_primary_filter"
              ]
            }
          },
          "char_filter": {
            "icu_normalizer_nfc": {
              "type": "icu_normalizer",
              "name": "nfc"
            }
          },
          "filter": {
            "icu_collation_primary_filter": {
              "type": "icu_collation",
              "strength": "primary"
            }
          }
        }
      }
}'


curl -XPUT 'http://localhost:9200/icu_wildcard/_mapping/test?pretty=1' -d '
{
    "dynamic": false,
    "_source": {
      "enabled": false
    },
    "properties": {
      "first_name_unicode": {
        "type": "string",
        "analyzer": "unicode_l1"
      },
      "first_name_standard": {
        "type": "string",
        "analyzer": "standard"
      }
    }
  }
}'

echo "==== Adding doc ===="
curl -XPUT 'http://localhost:9200/icu_wildcard/test/1?pretty=1' -d '{
    "first_name_unicode" : "ABCDEFGHIJKLabcdefghijkl",
    "first_name_standard" : "ABCDEFGHIJKLabcdefghijkl"
}'

curl -XPOST 'http://localhost:9200/icu_wildcard/_flush?pretty=1'

echo "==== Search on icu field ===="
curl -XGET 'http://localhost:9200/icu_wildcard/test/_search?q=first_name_unicode:abcdef*&analyze_wildcard=true&pretty=1'
echo "==== Search on standard field ===="
curl -XGET 'http://localhost:9200/icu_wildcard/test/_search?q=first_name_standard:abcdef*&analyze_wildcard=true&pretty=1'

echo "==== Query explain ===="
curl -XGET 'http://localhost:9200/icu_wildcard/test/_validate/query?explain&q=first_name_unicode:abcdef*&analyze_wildcard=true&pretty=1'
curl -XGET 'http://localhost:9200/icu_wildcard/test/_validate/query?explain&q=first_name_standard:abcdef*&analyze_wildcard=true&pretty=1'