Attributes not used when search is anonymous

We have configured our LDAP module of our Matrix server like this :

modules:
  - module: "ldap_auth_provider.LdapAuthProviderModule"
    config:
      enabled: true
      mode: simple
      uri: 
         - "ldaps://xxx:636"
      validate_cert: true
      base: "ou=users,dc=xxx.internal,dc=local"
      attributes:
        uid: "uid"
        mail: "mail"
        name: "cn"
        
      filter: "(&(|(objectclass=xxx))(|(memberof=cn=user,ou=groups,dc=xxx.internal,dc=local)))"
      group_filter: "(&(|(objectclass=xxx)))"
      allow_empty_password: false

However we observe that uid, mail and cn are not retrieved from the LDAP server, while they are retrieved when we set bind_dn and bind_password.

Is it expected?
Is it possible to do anonymous requests and still retrieve attributes for mapping?

Thank you,

Start by examining the LDAP authentication module's handling of anonymous searches versus searches using bind_dn and bind_password, using the configuration in the issue as the reproduction case. Determine whether mapped uid, mail, and cn attributes are expected to be returned anonymously, and document or test the supported behavior.