Q: Are 1:1 associations supposed to be mirrored in class table inheritances?

[R3dLantern]

I use Sulu CMS and extend its User entity as per docs. For my use case, I need to split the user into admin and non-admin user, which I did using class table inheritance:

/**
 * @ORM\Table(name="se_users")
 * @ORM\Entity
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="user_type",type="string",length=15)
 * @ORM\DiscriminatorMap({
 *   "admin":"App\Entity\AdminUser",
 *   "nonadmin":"App\Entity\NonAdminUser"
 * })
 */
abstract class User extends SuluUser
{
    // ...
}

/**
 * @ORM\Table(name="proj_admin_users")
 * @ORM\Entity
 */
class AdminUser extends User
{
    // ...
}

/**
 * @ORM\Table(name="proj_nonadmin_users")
 * @ORM\Entity
 */
class NonAdminUser extends User
{
    // ...
}

Sulu\Bundle\SecurityBundle\Entity\User is configured via .orm.xml file, stating a 1:1 association to the table co_contacts on its $contact property:

<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
    <mapped-superclass name="Sulu\Bundle\SecurityBundle\Entity\User" table="se_users">
        <!-- ... -->
        <one-to-one field="contact" target-entity="Sulu\Bundle\ContactBundle\Entity\ContactInterface">
            <join-column name="idContacts" referenced-column-name="id" on-delete="CASCADE" nullable="false"/>
        </one-to-one>
        <!-- ... -->
    </mapped-superclass>
</doctrine-mapping>

When creating a new migration class, the SQL statements for creating proj_admin_users and proj_nonadmin_users contain not only an FK-referenced id column, but also an FK-referenced idContacts column that mirrors the column in se_users:

$this->addSql('CREATE TABLE proj_admin_users (id INT NOT NULL, idContacts INT NOT NULL, UNIQUE INDEX UNIQ_AAAAAAAAAAAAAAAA (idContacts), PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8mb4 COLLATE `utf8mb4_unicode_ci` ENGINE = InnoDB');
$this->addSql('ALTER TABLE proj_admin_users ADD CONSTRAINT FK_AAAAAAAAAAAAAAAA FOREIGN KEY (idContacts) REFERENCES co_contacts (id) ON DELETE CASCADE');
$this->addSql('ALTER TABLE proj_admin_users ADD CONSTRAINT FK_BBBBBBBBBBBBBBBB FOREIGN KEY (id) REFERENCES se_users (id) ON DELETE CASCADE');

However, fetching of the inheriting entities fails due to class metadata handling seemingly cancelling out their idContacts columns.

Is the behaviour of creating mirroring 1:1 columns in class table inheritances an intended feature?