user_profile_form_validate() is always called, even when $category != 'account'

This function only performs entity_form_field_validate('user', $form, $form_state);, which will validate the user account bundle, which is not there when $category != 'account'.

function user_profile_form($form, &$form_state, $account, $category = 'account') {
  ...
  $form['#user_category'] = $category;

  if ($category == 'account') {
    user_account_form($form, $form_state);
    // Attach field widgets.
    field_attach_form('user', $account, $form, $form_state);
  }
  ...
  $form['#validate'][] = 'user_profile_form_validate';
  // Add the final user profile form submit handler.
  $form['#submit'][] = 'user_profile_form_submit';

  return $form;
}

/**
 * Validation function for the user account and profile editing form.
 */
function user_profile_form_validate($form, &$form_state) {
  entity_form_field_validate('user', $form, $form_state);
}

This can lead to errors during validation as these fields are still validated. See #1200890: Fields that trigger errors using hook_field_validate() trigger PHP errors