Register a user without email verification should still send an email

I believe this being a follow up to #2291055: REST resources for anonymous users: register.

When registering a user via the UserRegistrationResource REST endpoint, with email verification disabled (verify_mail = FALSE) and no administrative approval required the expected register_no_approval_required email notification is not sent.
In contrast, when registering a user via the Drupal UI under the same configuration and as an anonymous user, the register_no_approval_required notification is sent as expected.

This inconsistency suggests that the REST resource is not aligning with the intended behavior implemented in the RegisterForm logic.

I am creating an user with the rest resource, configured not to verify email address, and the register_no_approval_required is not sent.

However, registering the user with the same settings through the drupal UI as an anonymous user does send the notification.

One would expect the same behavior:

./core/modules/user/src/RegisterForm.php
<?php
    // No email verification required; log in user immediately.
    elseif (!$admin && !\Drupal::config('user.settings')->get('verify_mail') && $account->isActive()) {
      _user_mail_notify('register_no_approval_required', $account);
      user_login_finalize($account);
      drupal_set_message($this->t('Registration successful. You are now logged in.'));
      $form_state->setRedirect('<front>');
    }
?>

./core/modules/user/src/Plugin/rest/resource/UserRegistrationResource.php:

<?php
  protected function sendEmailNotifications(UserInterface $account) {
    $approval_settings = $this->userSettings->get('register');
    // No e-mail verification is required. Activating the user.
    if ($approval_settings == USER_REGISTER_VISITORS) {
      if ($this->userSettings->get('verify_mail')) {
        // No administrator approval required.
        _user_mail_notify('register_no_approval_required', $account);
      }
    }
    // Administrator approval required.
    elseif ($approval_settings == USER_REGISTER_VISITORS_ADMINISTRATIVE_APPROVAL) {
      _user_mail_notify('register_pending_approval', $account);
    }
  }

?>

Steps to Reproduce
Set the following user settings in Drupal:
- Who can register accounts? → Visitors
- Require email verification → Disabled
Enable the User Registration REST resource and allow anonymous access.
Perform a POST request to /user/register via REST to create a new user.
Observe that:
- The user is created and marked active.
- No email is sent to the user (register_no_approval_required not triggered).
Now, go to the Drupal frontend and register a user with the same configuration.
The expected email is sent.