Order view: Sort by order number does not sort numerically

The Commerce Order Number field is a string field. So, it will work similarly to a string even though it was used as an integer number. So, it works as designed.

Drupal\commerce_order\Entity\Order.php

$fields = parent::baseFieldDefinitions($entity_type);

    $fields['order_number'] = BaseFieldDefinition::create('string')
      ->setLabel(t('Order number'))
      ->setDescription(t('The order number displayed to the customer.'))
      ->setRequired(TRUE)
      ->setDefaultValue('')
      ->setSetting('max_length', 255)
      ->setDisplayConfigurable('form', TRUE)
      ->setDisplayConfigurable('view', TRUE);

    $fields['version'] = BaseFieldDefinition::create('integer')

To achieve the sorting as Integer we can able to use Query alter to type cast string as Integer. Below is an example.

use Drupal\views\ViewExecutable;
use Drupal\views\Plugin\views\query\QueryPluginBase;

/**
 * Implements hook_views_query_alter().
 */
function example_views_query_alter(ViewExecutable $view, QueryPluginBase $query) {
  if ($view->id() == 'VIEW_ID') {
    // Alter Commerce order to sort based on Order number.
    $formula_form = "CAST(order_number AS SIGNED)";
    $query->addField(NULL, $formula_form, 'order_number_field');
    $query->addOrderBy(NULL, NULL, 'DESC', 'order_number_field');
  }
}

This is a feature request not a bug report. I'm aware of why it doesn't sort correctly. I want to implement smart sorting as a feature at some future point. If this is not a feature the commerce maintainers want in commerce core then they can say so and close this as Won't Fix