mailchimp_auth_newsletter_form does not show interests group during sign up

In version 2.3, the code is:
if (variable_get('mailchimp_interest_groups_user_forms', FALSE) && isset($memberinfo['merges']['GROUPINGS'])) {
$interests = _mailchimp_interest_groups_element($q, $list->id, $memberinfo['merges']['GROUPINGS'], $is_subscribed);

In version 2.2, the code is:
if (variable_get('mailchimp_interest_groups_user_forms', FALSE)) {
$interests = _mailchimp_interest_groups_element($q, $list->id, $memberinfo['merges']['GROUPINGS'], $is_subscribed);

Because during signup, $memberinfo['merges']['GROUPINGS'] is not set, the interest group is no longer shown. Why is that? I'd like to let user select interest groups during sign up.

If we change back to 2.2 version, the interest group can be shown. Why is the change made?