wc-order-emails-purchase-notes-for-admins.php

<?php // only copy if needed

/**
 * Only adds purchase notes to admin order emails
 */
function sww_purchase_notes_for_admin_emails_only( $args ) {
  
    $args['show_purchase_note'] = $args['sent_to_admin'];
    return $args;
}
add_filter( 'woocommerce_email_order_items_args', 'sww_purchase_notes_for_admin_emails_only' );