Doc values are not enabled by default

Elastic Stack Elasticsearch
1

The deep dive on doc values article says that

"Doc values are enabled by default for all fields except analyzed strings"

However, when looking at the field data usage I'm seeing fields that are set to "not_analyzed" consuming field data memory.

GET /_stats/fielddata?fields=*
"gh9": {
    "memory_size_in_bytes": 601821608
},

My template

"gh9": {
     "index": "not_analyzed",
     "type": "string"
}

Our Elasticsearch version is 2.4.1.

Do you know why it appears that this non_analyzed string is consuming field_data memory?

2

see here: Not_analyzed field with doc_values still in fielddata cache