So by looking a bit more patiently in the documentation, i noticed this section:

sqlalchemy_session_persistence
Control the action taken by sqlalchemy_session at the end of a create call.

Valid values are:

None: do nothing

'flush': perform a session flush()

'commit': perform a session commit()

The default value is None.

Why the hell the default option is 'None'? I don't know. But just by setting it manually to 'commit' the data started being saved on database.