Same Term not added and no warning

1. Head to the native Post type “Posts.”:
wp-admin/post.php?post=1&action=edit.
2. Add a new term to the Categories meta box.
3. Save it (It appears on top of the list with the check mark).
4. Add the same term again ==> nothing happens, and the term is (obviously) not added.

What I expect is a warning that the term exists already, just as in the Categories Edit Screen (wp-admin/edit-tags.php?taxonomy=category):
>A term with the name provided already exists with this parent.

Anyone here agrees to file this at least as an UX Issue?

Thanks for your opinion (or eventual explanation why we should not have a notice there.