Solution:
You can use WordPress '__return_empty_string' with woocommerce_checkout_get_value WooCommerce filter hook to get empty values simply this way:
add_filter('woocommerce_checkout_get_value','__return_empty_string', 1, 1);
This will empty all checkout values, when checkout page is loaded.
The Code goes in functions.php file of your active child theme (or theme) or also in any plugin file.
This code is tested and works.
You should reset all existing sessions in Woocommerce settings > System status > tools and also the cache if your e-commerce use any.
Also empty your browser cache and stored data.