Woocomerce add info after order email prouct item

you can do this with a differnent woocommerce hook:

woocommerce_order_item_meta_end ($item_id, $item, $order, $plain_text)

use it similarly to the cart filter above.

For a visual representation if you want the additional information somewhere else see this link:

https://businessbloomer.com/woocommerce-visual-hook-guide-emails/

You can also always go right to the source and see all the hooks/filters/actions in woocommerce:
https://docs.woocommerce.com/wc-apidocs/hook-docs.html

as an example:

add_action( 'woocommerce_order_item_meta_end', 'rt_order_item_meta_end', 10, 4 );
function rt_order_item_meta_end( $item_id, $item, $order, $plain_text ){
    echo '<p>cool item detail</p>';
}