Extending Structure as a Custom field - Multiple translation issues

Firstly noticed in 4.0.1
upgraded to 4.0.2 no changes.

I can make a structure show the right label related to a field depending on the right language.

This is what I get :

My Blueprint

  registration:
    label:
      fr: Inscription
      en: Registration
    type: registration
    fields:
      firstname:
        label:
          fr: Prénom
          en: First name
        type: text
      lastname:
        label:
          fr: Nom
          en: Last name
        type: text
      email:
        label:
          fr: Email
          en: Email
        type: text
      semester:
        label:
          fr: Votre semestre courant
          en: Your current semester
        type: select
        options:
          one:
            en: 1st
            fr: 1er
          two:
            en: 2nd
            fr: 2ème
          three:
            en: 3rd
            fr: 3ème
          four:
            en: 4th
            fr: 4ème
      timestamp:
        label:
          fr: Date d'inscription
          en: Registration date
        type: date
        time: true
        default: now
        readonly: true

Also, selection options are not being populated at all in the “add” form

Looks like a custom field? Do you get the same error with a standard structure field?

I’m stupid af…

Yep you are right, no error with the native structure field.

Added

    'fields' => [
        'registration' => [
            'extends' => 'structure',
...

And everything works fine now !