How to get identities access_token inside an Action

This page suggests that if I return an access_token and refresh_token in login custom script, the user profile will contains the linked identity.

I can’t find how I can retreive that information inside an Custom post-login action.
event.user.identities only contains basic connection fields:

{ connection: 'custom-backend', isSocial: false, provider: 'auth0', userId: 'custom|2000000|4', user_id: 'custom|2000000|4' }

I manage to get it using the management API. But it seems overkill.
Even the test sample in action contains an access token :thinking::

"user": {
    "app_metadata": {},
    "created_at": "2022-10-18T15:29:04.063Z",
    "email_verified": true,
    "email": "",
    "family_name": "Smith",
    "given_name": "John",
    "identities": [
        "connection": "Username-Password-Authentication",
        "isSocial": false,
        "provider": "auth0",
        "userId": "5f7c8ec7c33c6c004bbafe82",
        "accessToken": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gU21pdGgiLCJpYXQiOjE1MTYyMzkwMjJ9.Q_w2AVguPRU2KskCXwR7ZHl09TQXEntfEA8Jj2_Jyew",
        "profileData": {},
        "user_id": "5f7c8ec7c33c6c004bbafe82"