The documentation has long since been changed.

Note that the anon user is able to become root without a password by default, as a development convenience. To prevent this, remove anon from the wheel group and it will no longer be able to run /bin/su.

https://github.com/SerenityOS/serenity/commit/a2a6bc534868773b9320ec3ca7399283cf7a375b (this seems to have also switched to gender neutral language in other parts.'of the documentation and comments as well).

Original drama: https://github.com/SerenityOS/serenity/pull/6814