You should be able to use the woocommerce_customer_get_downloadable_products
filter and return the array of downloads in reversed order.
function reverse_my_downloads_order( $downloads ) {
return array_reverse( $downloads );
}
add_filter( 'woocommerce_customer_get_downloadable_products', 'reverse_my_downloads_order' );
Add this code to your functions.php file of your active child-theme or theme. I didn’t test it, but it should work.