the option malloc_version in document not exist in mariadb

In doc https://mariadb.com/kb/en/mariadb/documentation/optimization-and-tuning/system-variables/server-system-variables/#malloc_version

malloc_version

Description: Version of the used malloc library.
Scope: Global
Dynamic: No
Data Type: string
Introduced: MariaDB 10.0.8

but in mariadb ,no such option can find !
and i also find the same description but different option exist

https://mariadb.com/kb/en/mariadb/documentation/optimization-and-tuning/system-variables/server-system-variables/#version_malloc_library

version_malloc_library

Commandline: No
Description: Version of the used malloc library
Scope: Global
Dynamic: No
Type: string
Introduced: MariaDB 10.0.8

Mariadb (none)|mysql99.sock >select version();

+---------------------+

| version()           |

+---------------------+

| 10.0.12-MariaDB-log |

+---------------------+

1 row in set (0.00 sec)

Mariadb (none)|mysql99.sock >show variables like 'malloc_version';

Empty set (0.00 sec)