Woocommerce: Remove variant options from admin new order email

One approach would be to override woocommerce/templates/emails/email-order-items.php (and possibly the version for plain-text emails) with your own version. It has access to $sent_to_admin, so you could replace its call to echo wp_kses_post( apply_filters( 'woocommerce_order_item_name', $item->get_name(), $item, false ) ); with your own.