The limitation of --replicate-rewrite-db is under-documented on MariaDB. I only see it documented at https://mariadb.com/kb/en/mariadb/mysqld-options/#-replicate-rewrite-db, and it doesn't mention whether this option works with cross-database update or not, and what statement are not replicated.

I am not sure whether MariaDB has diverged from what MySQL has for this feature, but there should be some confirmation whether MariaDB still has the same limitation as in MySQL or not: https://dev.mysql.com/doc/refman/5.7/en/replication-options-slave.html#option_mysqld_replicate-rewrite-db