You won't see the red asterisk in the update screen as the field is non-editable.
The $fieldspec['table_id_jnr'] array contains the entry 'noedit' => 'y', which makes the field non-editable by default, but the 'Add Relationship' task should cause the following code to be executed in the dict_relationship_jnr class:
function _cm_changeConfig ($where, $fieldarray)
{
// make these fields editable
unset($this->fieldspec['database_id_jnr']['noedit']);
unset($this->fieldspec['table_id_jnr']['noedit']);
return $fieldarray;
} // _cm_changeConfig