Custom Message from Jetpack Publicize – WordPress Development Stack Exchange

I'm using the following code to add a # character to each word (except the 1st) in the title, then to set this as the shared post message.

function set_jetpack_publicize_default_message () {
global $ post;
if (! empty ($ post-> ID)) {
if (! $ wpas_title = get_post_meta ($ post-> ID, & # 39; _wpas_mess & # 39 ;, true)) {
$ wptitle = get_the_title ();
$ wptitlenew = str_replace (& # 39; & # 39 ;, & # 39 ;, $ wptitle);
update_post_meta ($ post-> ID, & # 39; _wpas_mess & # 39 ;, $ wptitlenew);
}
}
}
add_action (& # 39; publicize_save_meta & # 39 ;, & # 39; set_jetpack_publicize_default_message & # 39;);
add_action (& # 39; post_submitbox_misc_actions & # 39 ;, & # 39; set_jetpack_publicize_default_message & # 39;);

It works in the administration area of ​​WP, as seen below:
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However, when the publication is shared by Jetpack, the message is not the personalized Message of the publication. As seen below:
enter the description of the image here

What's wrong with the code? Should not it work already? From my understanding, update_post_meta I should do the trick and use my custom message for the Jetpack shared resources.
If it matters, I am in the latest version of WordPress (4.9.8), and the publications are of a custom type ("product"). I have tried adding the code to the functions.php file and the Custom Snippets add-on, but the result is the same. Although it displays the custom message in the WP publication editor, it does not use it when Jetpack shares the publication.

Any ideas?