_split index API issues

Hi,

I have done a split index query on one of the filebeat indices.
What I observe is, as the documentation mentions (Split index API | Elasticsearch Guide [8.2] | Elastic) once the documents are copied into another shard of destination index, the source documents are deleted. But in my case that has not happened. Any idea why that might be so?

My index details
source index:
name - filebeat-7.17.3-2022.05.11-000001
replicas - 1
shards - 3
documents - 81013018
size - 63.9gb

destination index
name filebeat-7.17.3-2022.05.11-000001_1
replicas - 1
shards - 3
documents - 81013018
size - 63.9gb

If you can see here, source and destination indices are of same size and configuration.

API call that I did:

PUT /filebeat-7.17.3-2022.05.11-000001/_settings
{
  "settings": {
    "index.blocks.write": true
  }
}
POST /filebeat-7.17.3-2022.05.11-000001/_split/filebeat-7.17.3-2022.05.11-000001_1
{
  "settings": {
    "index.number_of_shards": 3
  }
}

The docs say;

  1. Hashes all documents again, after low level files are created, to delete documents that belong to a different shard.

It does delete the original index, that's something you need to request.