Why elasticsearch automatically creates an index if it has not been created before delete operation?

I have confused about the description about the delete API that the delete operation automatically creates an index if it has not been created before. But i tried to execute the delete an unexisting index operation, the elasticsearch response error directly and I didn't see that index has been created. Is there any one know this question. If it really works in that way,why did the delete operation create the index at first?

I just tried and it does not do this behaviour;

$ curl -XDELETE 0:9200/testindex
{"error":{"root_cause":[{"type":"index_not_found_exception","reason":"no such index","resource.type":"index_or_alias","resource.id":"testindex","index_uuid":"_na_","index":"testindex"}],"type":"index_not_found_exception","reason":"no such index","resource.type":"index_or_alias","resource.id":"testindex","index_uuid":"_na_","index":"testindex"},"status":404}

I tried to delete an unexisting index and got the same response as you,so I doubt about that description of official doc which as follows
https://www.elastic.co/guide/en/elasticsearch/reference/5.x/docs-delete.html#delete-index-creation
why delete an unexisting index will create it .It dosen't make any sense....