Updating the note on comparing merge request versions

doc/user/project/merge_requests/versions.md

@@ -64,9 +64,10 @@ In GitLab 12.10, we added a comparison mode, which
 shows a diff calculated by simulating how it would look like once merged - a more accurate
 representation of the changes rather than using the base of the two
 branches. The new mode is available from the comparison target drop down
-by selecting **master (HEAD)**. In the future it will
-[replace](https://gitlab.com/gitlab-org/gitlab/-/issues/198458) the
-current default comparison.
+by selecting **master (HEAD)**. In GitLab 13.9, it 
+[replaced](https://gitlab.com/gitlab-org/gitlab/-/issues/198458) the
+old default comparison. For technical details, additional information is available in the
+[developer documentation](../../../development/diffs.md#merge-request-diffs-against-the-head-of-the-target-branch).
 
 ![Merge request versions compare HEAD](img/versions_compare_head_v12_10.png)