--lock-tables is enabled by default for mysqldump. --single-transaction offers a way to get a consistent dump without locking tables, but the tables have to support transactions (which InnoDB does and MyISAM does not). You should probably use
--single-transaction if you can.
The
mediawiki.org article you reference tries to ensure consistency by having you set $wgReadOnly to prevent writes to the database (at least from within MediaWiki core). I'm not sure how much effect it actually has, given that --lock-tables is enabled by default, but it's been on the page for 15 years, so it must be right. :)