What is "optional" about autocreated guest checkout?

I too am wondering what is 'optional' about an account that will surely be created without the user doing anything about it.

I have been searching through the variables on the form and don't seem to see a way to override the text. Is there a way please? I want to set "Proceed to checkout, an account will be created for you at the end. You will be notified via email about your new account."

For anyone else looking to override this text, you can put this on a custom module or .theme file,

/**
 * Implements hook_form_alter().
 */

function custommodule_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
          //Override 'Proceed as guest' text
          $form['login']['guest']['text']['#markup'] = t('<p>Proceed to checkout, an account will be created for you at the end. You will be notified via email about your new account.</p><p>You can also proceed as guest if you have an existing account and your new order will be added to your account.</p>');
}