Content Sections area empty if any template is chosen (Mailchimp free plan)

Debugging mailchimp_campaign\Form\MailchimpCampaignForm::form at line 251 where the content sections should be found and listed. As expected $mc_template->info->sections is empty

foreach ($mc_template->info->sections as $section => $content) {

where $mc_template was generated from $mc_template = mailchimp_campaign_get_template($form_state->getValue('template_id'));

mailchimp_campaign_get_template is in mailchimp_campaign.module and relevant code is:

          $template->info = $mc_templates->getTemplateContent($template_id);
          $tags = ['cache_mailchimp'];
          \Drupal::cache()->set('template_' . $template_id, $template->info, CacheBackendInterface::CACHE_PERMANENT, $tags);

Tried this with a different client that has a paid Mailchimp account and a "code-your-own" template. The sections look like this

<div mc:edit="preheader_leftcol_content"><p>Some content here.</p></div>

And these sections do populate the Content Sections area of the Drupal form.

So, it looks like this module will only work with paid Mailchimp accounts. I feel like that should be noted or highlighted on the campaign form.

Suggested fix for the form description

Change from:

"Select a Mailchimp user template to use. Due to a limitation in the API, only templates that do not contain repeating sections are available. If empty, the default template will be applied."

To:

"Select a Mailchimp user template to use. Due to a limitation in the API, only templates that do not contain repeating sections are available. If empty, the default template will be applied. Only templates built using Mailchimp's "Code Your Own" feature will be able to have content added here."