concise error messages.
otherwise it hits all the same back end stuff. It just happens to be a consistent interface to it (along with all node forms)
BTW: if a form is not programmatically submittable, it should be consired a bug, please make an issue for it.
there are a handful of forms like this at the moment, but i wasn't aware that node form was one of them.
(it was working in my tests here : drupal.org/node/79900)