[WooCommerce BR] Keep shipping fields from being fed with billing values:

functions.php

<?php

function wcbr_disable_copy_shipping_from_billing_fields( $default, $input ){

    if( 0 === stripos($input, 'shipping_') ){
        $default = '';
    }

    return $default;

}

add_filter('woocommerce_checkout_get_value', 'wcbr_disable_copy_shipping_from_billing_fields', 10, 2);