Functions _cck_signup_validate_signup_node, cck_signup_cck_signup_validate & Module cck signup validate has similar functionalit

These two functions have the same purpose if i'm right that is validating of current signup. In my opinion there's no need for two finctions.
I would just have

function _cck_signup_validate_signup_node($form, &$form_state) {
  // Allow modules to easily validate event sign-ups.
    foreach (module_implements('cck_signup_validate') as $module) {
      $function = $module . '_cck_signup_validate';
      $function($type, $event, $form_state);
    }
}

And I would put any validation into 'function cck_signup_cck_signup_validate'. Or Creating separate submodules for each validation.
Actually we've got a submodule 'cck signup validation' that should have all these validations probably. That's what it's name stands for isn't it.