Attribute based mapping ignores FieldIndexOption value

Elastic Stack Elasticsearch
1

I have a class as follows

    [ElasticsearchType(Name = "foo", IdProperty = "Id")]
    public class Foo
    {
        [String(Index = FieldIndexOption.NotAnalyzed)]
        public Guid Id { get; set; }
    }

and on index, mapping is

{
    "mappings": {
      "foo": {
        "properties": {
          "id": {
            "type": "string"
          }
        }
      }
    }
}
```