Underscores in Boxes class names

Is this intentional?

See:

/**
 * Theme function for the form.
 */
function theme_boxes_box($block) {
  $output = "<div id='boxes-box-" . $block['delta'] . "' class='boxes-box" . (!empty($block['editing']) ? ' boxes-box-editing' : '') . "'>";
  $output .= '<div class="boxes-box-content">' . $block['content'] . '</div>';
  if (!empty($block['controls'])) {
    $output .= '<div class="boxes-box-controls">';
    $output .= $block['controls'];
    $output .= '</div>';
  }
  if (!empty($block['editing'])) {
    $output .= '<div class="box-editor">' . $block['editing'] . '</div>';
  }
  $output .= '</div>';
  return $output;
}

Would it make sense to run $block['delta'] through something like: str_replace('_', '-', $block['delta'])?