Example of how to update postmeta on a new product.

update_postmeta_for_products.php

<?php
function add_this_to_new_products( $product_get_id ) {

	$productType = WC_Product_Factory::get_product_type( $product_get_id);
	if( $productType == 'registrations')  {
		update_post_meta( $product_get_id, '_tax_status', 'none' );
	}

}

add_action( 'woocommerce_update_product', 'add_this_to_new_products', 10, 1 );

This example is changing tax status to none on product type of registrations.