Correct the documentation for create_doc privilege

docs/reference/docs/index_.asciidoc

@@ -45,7 +45,8 @@ include::{docdir}/rest-api/common-parms.asciidoc[tag=if_primary_term]
 (Optional, enum) Set to `create` to only index the document
 if it does not already exist (_put if absent_). If a document with the specified
 `_id` already exists, the indexing operation will fail. Same as using the
-`<index>/_create` endpoint. Valid values: `index`, `create`. Default: `index`.
+`<index>/_create` endpoint. Valid values: `index`, `create`.
+If document id is specified, it defaults to `index` or else it defaults to `create`.
 
 include::{docdir}/rest-api/common-parms.asciidoc[tag=pipeline]
 

x-pack/docs/en/security/authorization/privileges.asciidoc

@@ -171,10 +171,13 @@ Privilege to index documents. Also grants access to the update mapping action.
 However, it does not enable a user to update existing documents.
 +
 --
-NOTE: When indexing documents with an external `_id` either via the index API or
-the bulk API, the request must use `op_type` as `create`. If `_id`s are
-generated automatically, the authorization happens as if the `op_type` is set to
-`create`.
+NOTE: This privilege relies on the `op_type` of indexing requests via <<docs-index_,Index API>>
+or <<docs-bulk,Bulk API>>.
+When ingesting documents as a user who has the `create_doc` privilege (and no higher privilege
+such as `index` or `write`), the `op_type` can be set to `create` through one of the following:
+1. Explicitly setting the `op_type` parameter
+2. Calling the `_create` endpoint
+3. Creating a document with an auto-generated `_id`
 
 --