Can't reference entities' ID inside a Fixtures Set

I'm trying do achieve the following tricks.

[From the Alice 1.x documentations](https://github.com/nelmio/alice/tree/1.x#references):

> You can reference entities' ID but you will then have to split fixtures in multiple files (this is because objects are persisted at the end of each file processing) :

``` yaml
# fixture_user.yml
Nelmio\Entity\User:
# ...
```

``` yaml
# fixture_group.yml
Nelmio\Entity\Group:
group1:
name: Admins
owner: @user1->id
```

---

Maybe there is something I miss but it look like objects are not persisted at the end of each file when I use Fixtures Set. Is it true or what did I miss ?