Desactivar el autorelleno de campos en checkout

Agregar el sgte código al functions

add_filter('woocommerce_checkout_get_value','__return_empty_string',10);

Para filtrar sólo algunos campos, agregar un callback

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

function radar_remove_values( $value, $input ) {
    $item_to_set_null = array(
            'billing_first_name',
            'billing_last_name',
            'billing_company',
            'billing_address_1',
            'billing_address_2',
            'billing_city',
            'billing_postcode',
            'billing_country',
            'billing_state',
            'billing_email',
            'billing_phone',
            'shipping_first_name',
            'shipping_last_name',
            'shipping_company',
            'shipping_address_1',
            'shipping_address_2',
            'shipping_city',
            'shipping_postcode',
            'shipping_country',
            'shipping_state',
        );

    if (in_array($input, $item_to_set_null)) {
        $value = '';
    }

    return $value;
}