Access databases from command line failed when grants set with wildcarded hosts

We have used the wildcard capability with grants in our current MySQL setup, using grants such as

grant all on `%user%`.* to 'user'@'%' identified by 'somepassword';

If we try this with the command line client pointed at a maxscale host, specifying a database gives us an 'access denied' failure.

mysql -h maxscale_host -u user -p user_db

whereas connecting to one of the Galera nodes directly works

mysql -h galera_host -u user -p user_db

If we explicitly set the grant for a specific database, then the client works

grant all on `user_db`.* to 'user'@'%' identified by 'somepassword';

In all cases, connecting without specifying the database and then choosing the database with a use statement works.