Access Denied: User without global privileges on a schema but with grants only on some tables can't connect if the default schema is specified in the connection string

If a user has only privileges on some objects/tables of a schema, he can't connect by specifying such schema as default schema for the connection:
If the schema is not specified, it can connect regularly.

MySQL [(none)]> show grants for 'pippo'@'%';
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Schema specified:

$ mysql -upippo -p123 -h127.0.0.1 -P4006 db3
ERROR 1045 (28000): Access denied for user 'pippo'@'127.0.0.1' (using password: YES) to database 'db3'

No schema specified:

$ mysql -upippo -p123 -h127.0.0.1 -P4006
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MySQL connection id is 2485
Server version: 10.0.0 1.4.3-maxscale MariaDB Server, wsrep_25.13.raf7f02e

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MySQL [(none)]>