Array Sort Script to sort array by index

Elastic Stack Elasticsearch
1 
PUT /my-index-000001/_doc/1?refresh
{
   "product": "chocolate",
   "salesManager" :["a","z","r"]
}

PUT /my-index-000001/_doc/2?refresh
{
   "product": "chocolate",
   "salesManager" :["v","f","d"]
}

PUT /my-index-000001/_doc/3?refresh
{
   "product": "chocolate",
   "salesManager" :["z","a","a"]
}

POST /my-index-000001/_search
{
   "sort": {
    "_script": {
      "type": "String",
      "script": {
        "lang": "painless",
        "source": "if(doc['salesManager'].size()>0) { return doc['salesManager'][0].toLowerCase()} return 'z';",
        "params": {
          "factor": 1.1
        }
      },
      "order": "asc"
    }
  }
}

I need to sort asc the index data using salesManager 0th index sort
so the correct sort order is on doc id is 1->2->3

but I am getting 3->2->1

2

Accessing 0th Index in painless is giving the value after sorting that field.
Why Array of Strings are getting sorted automatically ?

3

Hi @Dakshay_Agarwal

Maybe someone from the Elastic team can confirm but according to this doc there is an explanation for the behavior of your query.