Product Category Not Populating Taxonomy Terms on Product Variations

It looks like the taxonomy term fields of custom product variations (product types) are not apearing correctly.
Could you confirm this by adding a Term Reference field to the default Drupal Commerce Product variation (Machine name: product)?
The fields from the 'product' product vatiation will probably show up for every product variation now.
That is not supposed to happen. Every product variation should list its own Term Reference Fields.

The problem probably has to do with the query in
commerce_mailchimp_admin.inc

foreach (commerce_product_types() as $type => $product_type) {
    $instances = field_info_instances('commerce_product', 'product');
    $options = array('' => '- None -');
    foreach ($instances as $instance) {
      $field_info = field_info_field($instance['field_name']);
      if ($field_info['type'] == 'taxonomy_term_reference') {
        $options[$instance['field_name']] = $instance['label'];
      }
    }
    $form['order']['product']['commerce_mailchimp_category_field_' . $type] = array(
      '#type' => 'select',
      '#title' => $product_type['name'],
      '#options' => $options,
      '#default_value' => variable_get('commerce_mailchimp_category_field_' . $type, ''),
    );
  }

Thanks!
This is a bug. Here's the patch. And it's committed.

Tested the patch: it works perfectly with different term reference fields on multiple product variations.
Thanks Hibersh.