Comments - Replication and Binary Log System Variables
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Found the answer here, it does log all columns (in MySQL, and by logical extension MariaDB) before this parameter was supported:
https://dev.mysql.com/doc/refman/5.6/en/replication-options-binary-log.html#sysvar_binlog_row_image quoted below:
"The default value is full. In MySQL 5.5 and earlier, full row images are always used for both before images and after images."